What does 는 mean in 믿는다?

Question

In the following sentence:

회사원이 연구를 믿는다.

I don't understand what 는 means here. At least I understand that the verb is 믿다 and the meaning is "The employee believes the research.".

But what does the 는 mean?

Answer 1

It is the conjugated form of 믿다 in the formal non-polite (해라체) form, in the present tense, in the indicative (non-interrogative/non-question) mood.

Why does it have to insert a 는? Maybe one could think that it is like 밝다, which doesn't change in the conjugation for present indicative 해라체.

But this is one of key grammatical differences between verbs (동사) and adjectives (형용사) in Korean; verbs have to insert something (either 는 or ㄴ, depending on consonant or vowel before it) in this form, whereas adjectives don't insert anything.

Note this runs parallel to, but is not the same as, 는데 vs ㄴ데 for verbs vs adjectives.