Question words can be divided into two groups: simple question words and wh-phrases. The simple forms are a fixed list of five: wa who, wat what, hokker which, wêr where and hoe how. The examples in (5) illustrate the usage of these forms:

If the interrogative heads an embedded question, the clitical element 't is added, a reduction of the complementizer oft whether:

More on complementizers (whether or not as clitics) following interrogative pronouns is to be found in the syntactic part.

In the list below, some of these simple forms are discussed in more detail.

• The question-word wa who can have genitive case, resulting in the interrogative possessive pronoun waans? whose?, as in (7):
  Example 7

  
  

  Waans hûs is dat?

  whose house is that

  Whose house is that?

  An alternative formulation is with wa plus a possessive pronoun:
  Example 8

  
  

  Wa syn hûs is dat?

  who his house is that

  Whose house is that?

  Wa can be used transitively with a complement that refers to a person, but only in questions expressing reproach Hoekstra (1996), as shown in (9):

  Example 9

  
  

  Wa minske docht soks no?

  who human does something-like-that now

  Which human being can do something like that?

  When asking about more than one person and informing about which indivuduals, one can say wa en wa? who and who?:
  Example 10

  
  

  Hja gongen nei Ljouwert ta. > Wa en wa?

  they went to Ljouwert to > who and who

  They went to Ljouwert. > Who?

• The question word wat what; what kind of has an extended form watte?, in which a suffix -e is added Hoekstra (1987:54). This form is used in exclamatives in particular. Hence, when someone says ik ha wat moais sjoen I saw something beautiful, one can ask wat? but not *watte?. The form watte is typically used when someone did not understand the speaker. In the same way, the -e can be added to wêr? where?, resulting in wêre?. Possible answers to watte? are dit(te) this or dat(te) that, and possible answers to wêre? are hjir(re) here and dêr(e) there (see demonstrative pronouns). An alternative to the suffix -e in the case of wêr is the addition of the adverb sa so: wêrsa?, also extended to wêrsanne. Possible answers may then be hjirsa or dêrsa.

  Wat may used attributively, then meaning 'what kind of' or 'which'. Examples are given in (11):

  Example 11

  
  

  a.	Wat man is dat?
  	what man is that?
  	What kind of man is he

  b.	Wat taal prate dy lju?
  	what language speak those people
  	Which language do those people speak?

  A longer expression with the same meaning is wat foar or wat foar in.

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  See for more details about the question word wat what: interrogative what + preposition as nominal quantifier.

• Next to the question word hokker which, also the form hok which exists, apparently without any semantic difference. This is illustrated in (12).
  Example 12

  
  

  a.	Fan hok boerd moat ik it iten krije?
  	of which plate must I the food get
  	From which plate must I get the food?

  b.	Fan hokker boerd moat ik it iten krije?
  	of which plate must I the food get
  	From which plate must I get the food?

  The word hok is special because it is inflected as an adjective; it reflects gender and number of the following noun. Singular neuter nouns require hok. Before common gender or plural nouns, the form is hokke. See the contrast in (13):

  Example 13

  
  

  a.	Hokke klean wienen foar him?
  	which.PL clothes.PL were for him
  	Which clothes were for him?

  b.	*Hok klean wienen foar him?
  	which.SG.N clothes.PL were for him
  	Which clothes were for him?

  The originally composite form hokker is not inflected, and can thus be used in every position:

  Example 14

  
  

  Hokker klean wienen foar him?

  which clothes were for him

  Which clothes were for him?

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  Dutch influence

  Hokker is mainly used in written language nowadays. In spoken language the complex expression watfoar is often used instead. Under the influence of Dutch the use of welke is also increasing.

• Hoe can also be combined with the indefinite article in a; however only if followed by a singular count noun (15a). Otherwise, it should be replaced by hok or inflected hokke. But when the noun is plural, this is ungrammatical (15b). Hoe'n how a can be replaced by hok(ker) which (15c) and (15d). Hok(ker) may also stand in front of a plural noun, as can be seen in (15d).
  Example 15

  
  

  a.	Hoe'n auto hat er kocht?
  	how.a car.SG has he bought
  	What kind of car did he buy?

  b.	*Hoe'n auto's hat er kocht?
  	how.a car.PL has he bought
  	What kind of cars did he buy?

  c.	Hokker auto hat er kocht?
  	which car.SG has he bought
  	What kind of / which car did he buy?

  d.	Hokker auto's hat er kocht?
  	which car.PL has he bought
  	What kind of / which cars did he buy?

  The distribution of hoe'n and hok/hokke is comparable to the demonstrativessa'n so a such and sok/sokke such/such.INFL such.

The inventory of complex forms is far more open-ended, as wêr can be combined with almost any adposition to create a complex question word. Moreover, the form hoe can be used to make question words with adjectives, for example hoelang how long, and hokker can be combined with any noun. A handful of frequent and well-established formations of this sort are considered univerbations and are spelled as one word (16a-c), while other combinations are regarded as separate words (d):

The form wêrom why may no longer be perceived as complex by many speakers. The form wannear when certainly is not (note also that they are translated as a simple wh-word in English).