This is the 31st most frequent Finnish word.
se
The Finnish word "se" means "it" or "that" in English.
The word 'se' refers to 'it', representing the subject of the sentence (the dog).
Se on koira.
It is a dog.
In this question, 'se' represents 'it', referring to an unspecified object or subject.
Missä se on?
Where is it?
In this example, 'sen' is the accusative form of 'se', used as the object of the action.