Mood is one of the conditions for clausehood. Different moods give rise to clauses of different mood types. For example,
(1) yòu kàndào yí-gè liàngdiǎn again see one-CLS bright spot ‘to see another bright spot’
Without clause mood, the sequence of words is only a clause-forming unit; it is not a clause. Imagine a situation in which A is telling B a fact: yòu kàndào yígè liàngdiǎn (‘I see another bright spot’.). The sequence carries the declarative mood (with its corresponding intonation), and a declarative clause comes into being. Imagine another situation in which several people are focusing their eyes on the distance. One of them, let’s say A, suddenly shouts: ‘ yòu kàndào yígè liàngdiǎn !’(‘I see another bright spot!’). The sequence takes the exclamatory mood (with its
corresponding intonation), thus an exclamatory clause is formed. If another one from the group, let’s say B, asks A, ‘ yòu kàndào yígè liàngdiǎn ?’(‘Did you see another bright spot?’), the same sequence carries the interrogative mood (with its corresponding intonation). An interrogative clause is thus formed.