Expressing an effective search query

Selection of search terms

To obtain high-quality search results, it is essential to thoroughly explore and define your topic, and then determine the appropriate keywords. You can use general search engines, reference works, and scientific/review journals for this purpose.

Once you have formulated a well-defined research question based on your objective or given topic, you can identify a limited number of key terms and complement them with translations, synonyms, and related terms to create a comprehensive set of search terms.

Always keep in mind some essential questions: What is your exact objective or assignment? What are the limitations or restrictions? How far should you go in searching for information on your topic? What is the deadline for completion?

Exploring and delimiting your topic

In the initial stage, you gather information about the topic to find relevant search terms and also to delineate and identify the possible subtopics it may contain.

You can do this by:

  • Using general search engines on the internet;
  • Consulting (online) reference works (encyclopedias, dictionaries...);
  • Reviewing scientific and/or review journals...

Tip: Search engines with clustering capabilities (like Carrot) are often helpful to quickly find subtopics related to a specific domain. These search engines display a list of subtopics or related subjects alongside the search results.

For inspiration, you can also utilize AI | Large Language Models (such as ChatGPT) to explore the various subfields of a topic. However, keep in mind the limitations of these tools: the responses are based on the available training data and may not always be entirely reliable.

Chat-GPT : subfields

Formulating your research question or problem statement

After the initial exploration and delimitation, you formulate your topic into a specific and well-defined research question that typically answers questions like 'Who?', 'What?', 'Where?', and 'When?'.

You also determine whether you opt for a qualitative approach, focusing on the analysis of textual data, or a quantitative approach, centering around numerical data, or a combination of both.

Your research question is further determined by the type of study you wish to conduct. It can be descriptive, comparative, evaluative, explanatory, or focused on trends and relationships.


Suppose you need to write a paper on the role of energy in animal behavior. Based on the exploratory phase and a few simple questions, you arrive at a clearly delimited research question.

The research question must not be too broad. For instance, "Birds' display behavior" is too general as a research question. By using question word questions (W-questions), you can arrive at a more specific research question.

  • Who? Birds
  • What? The energy costs of birds' display behavior
  • Where? Worldwide
  • When? During the mating or courtship season
  • Purpose of the work? Research question in behavioural ecology

Research Question: 'What are the energy costs of birds' display behavior during the mating season in terms of their energy budget?'


Especially in clinical and evidence-based research, your research question can also be formulated as a PICO(T) or PEO question. You consider the following:

  • Population | patient | problem: Which (sub)group of individuals, which problem, or which phenomenon are you studying?
  • Intervention or indicator: What intervention or factor(s) are you studying?
  • Comparison: Which group of individuals or phenomena are you using as a comparison? What are you taking into account?
  • Outcome (or interest): What is the expected result or goal?
  • Timeframe: Over what period | timespan does it apply?


How does regular physical activity (I) compared to no physical activity (C) influence glycemic control (O) over a period of 12 months (T) in adult patients with type 2 diabetes (P)?


  • Population: Which (sub)group are you studying?
  • Exposure to preexisting conditions: What conditions apply to this subgroup?
  • Outcome: What is the expected result or goal?


What is the effect of daily physical exercise (E) on academic performance (O) in school-going children (P)?

In your literature review, you will search for information on each of the queried factors.


To determine if you have a good research question, you can use the FINER framework (Hulley et al. (2007). Designing Clinical Research. Lippincott, Williams & Wilkins)

  • Feasible: Is the planned research feasible?
  • Interesting: Is the question interesting for the research community?
  • Novel: Does the research bring new insights?
  • Ethical: Are you not crossing ethical boundaries?
  • Relevant: Is your question relevant for the research community and other stakeholders?

In addition, these factors are also important to have a clear understanding of your assignment and goal:

  • Time: Searching for references and reading documents takes time, and you need to realistically allocate it for yourself.
  • Scope: Can you limit yourself to recent literature, or do you need to create an exhaustive bibliography and thus review older literature as well?
  • Task: Do you only need to collect literature, or do you also have to compare the found articles with each other critically?

From problem statement to key terms and search terms

By using the core concepts or keywords from your problem statement, you can conduct a highly focused search for the desired information.


  • Problem Statement: What are the costs of bird's courtship behavior during the mating season in terms of their energy budget?
  • Keywords: courtship behavior, birds, mating season, energy budget

The key is to find the most relevant information while minimizing irrelevant results by using as few search terms as possible.

You can create a high-performing set of search terms by supplementing the keywords from your problem statement with:

  • Translations;
  • Synonyms;
  • Derivatives (e.g. singular and plural forms);
  • Narrower and/or broader and/or related terms...

You can find inspiration in reference works and specialized dictionaries, but Large Language Models | AI can also help you generate a suitable list of search terms. However, caution is advised due to the limitations of these tools. The results are dependent on the available training data and should always be verified. The same caution applies to automatic translations of terms.

ChatGPT ) keywords

Tips to find relevant search terms

  • Explore your topic using general search engines, (online) reference works...
  • You may also consider using Large Language Models | AI to brainstorm suitable search terms. Always be mindful of the limitations of these tools, as their results heavily rely on the available training data and should be verified.
  • Use the correct terminology by employing (one of these) three methods:
  1. Two-phase searching:
    Example: You want to write a paper on Gilles de la Tourette syndrome.
    - Phase 1: Enter a term into Google that closely matches what you are looking for, such as 'Tourette.' You will see the term 'Tourette Syndrome' mentioned multiple times in the results. This is the scientific name for Gilles de la Tourette syndrome.
    - Phase 2: Search using the keywords 'Tourette Syndrome.'
  2. Use keywords from reliable reference works.
  3. Use keywords from a thesaurus.

Narrow down your search terms sufficiently; they should precisely describe the subject of your search to avoid an excessive number of irrelevant search results. For example, if you are looking for information on human anatomy, search for "human anatomy" (and possible synonyms) rather than just "anatomy."

Most search engines and database search functions ignore capitalization, accents, and punctuation.

Combining search terms

Combine your search terms with Boolean operators (AND, OR, NOT) to create an effective search query that you can use in a catalogue or database (e.g. the UHasselt Discovery Service).

Use truncation marks (wildcards) to find different variations of a search term (e.g. Herodot* for Herodotos and Herodotus or wom?n for woman and women).

Utilize quotation marks for exact word combinations (e.g. "Martin Luther King") and the advanced search functions of databases and catalogues. This allows you to search in different fields and filter your search results based on various criteria.

Boolean operators (AND, OR, NOT)

To find very specific and targeted information on your topic, you need to combine search terms deliberately. This can be done, among others, by using boolean operators (AND | OR | NOT).


AND Diagram

This allows you to search for information that contains both search terms. If you simply enter multiple search terms one after another, the search engine will automatically combine them using the Boolean AND operator. In mathematical terms, this is called the intersection.

  • Example: '"estrous cycle" AND birds'
  • Advantage: Many search results are relevant.
  • Disadvantage: Not all relevant search results are found with this method.


OR Diagram

This allows you to search for information that contains at least one of the search terms. In mathematical terms, this is called the union.

  • Example: '"estrous cycle" OR birds'
  • Advantage: Many relevant search results are found.
  • Disadvantage: It may also retrieve a significant number of irrelevant search results.


NOT Diagram

This allows you to search for information that contains the first search term but not the second search term. In mathematical terms, this is called the difference.

  • Example: '"estrous cycle" NOT birds'
  • Advantage: Fewer and more relevant search results.
  • Disadvantage: The risk of excluding relevant search results.

Please note:

  • Do not confuse this with everyday language. If you say 'I want to know everything about cats and dogs,' you are searching for information about cats or dogs or both. This 'AND' from everyday language corresponds to the Boolean OR operator.
  • Use capital letters for the operators; otherwise, the search function considers them as regular keywords.
  • When combining multiple Boolean operators, use parentheses. They prioritize the terms within the parentheses and clarify the search.
    For Google, only the minus sign is used, not NOT. For example, jaguar speed -car or pandas

diagrams boolean operators cat dog canary

Truncation marks (wildcards)

You should make use of a truncation or wildcard symbol to easily combine similar search terms. The two most important truncation symbols are:

* (asterisk)

The wildcard '*' is used to replace one or more characters. Usually, you can use this symbol only at the end of a word stem.

  • Example: 'appel*' for 'apple', 'apples', 'apple tree'...

? (question mark)

The wildcard '?' is used to replace one character. You can use this symbol at the end of a word and, in some databases, even in the middle of a word.

  • Examples: 'appel?' for 'apple' and 'apples' (but not for 'apple tree'); 'wom?n' for 'woman' and 'women'


The key is not to truncate a word too early or too late. If you are searching for information about obesity, it is best to type 'obes*' and not 'ob*'.

Please note: In a minority of available databases, the functions of * and ? may be reversed in a search query.

If you want to retrieve search results that must contain the entered search terms in the exact same order, place your search terms between "double quotation marks." This way, you can avoid irrelevant search results.

  • 'Martin Luther King' will give search results about Martin Luther King (20th century), but it may also include results about Martin Luther (16th century) in combination with some king.
  • "Martin Luther King" will only give search results about Martin Luther King (20th century).
  • "Martin Luther" NOT "Martin Luther King" will only give search results about Martin Luther (16th century), but it will exclude results about Martin Luther King (20th century).

Filters & specification of search fields


Filters are features that allow you to narrow down the search results in a search query. In online databases/catalogues, filters are usually available through the Advanced search option. Some common filters that you can find in the search function of almost every online database include:

  • Title
  • Author
  • Publisher
  • Publication date
  • Type of publication (article, book, dissertation, etc.)
  • The availability of other filters may vary depending on the database.

Specifying Search Fields

With advanced search, you can often search across different fields simultaneously. For example, you can search for a specific title by a certain author. Below is an example of using different search fields and filters in the search interface of JSTOR - advanced search:

JSTOR Advanced search