The term interrogative refers to a grammatical form that is specialized for the following main uses:
i) to ask whether a certain state of affairs holds
y/n
A: gianni arrive
B: yes
‘Did Gianni arrive?’ ‘Yes.’
ii) to elicit information from the addressee
wh
A: gianni buy what
B: water
‘What did Gianni buy?’ ‘Water.’
iii) to report a doubt:
wh
a. ix1 think palm_up gianni ix buy qartichoke palm_up
‘I wonder what Gianni bought.’
y/n
b. ix1 think ix gianni wine buy done
‘I wonder whether Gianni bought wine.’
It is possible to distinguish between: i) polar interrogatives (sometimes called yes/no interrogatives because they ask whether a certain state of affairs holds or not, so they are naturally answered by ‘yes’ or ‘no’), ii) alternative interrogatives, which present two or more options for the reply, and iii) content interrogatives, which elicit a more elaborate answer than ‘yes’ or ‘no’ because they are used to ask the addressee to fill in some specific missing information.