verb
not used in progressive tenses -lieves; -lieved; -lieving
[+ obj] to accept or regard (something) as true
to accept the truth of what is said by (someone)
[+ obj] :to have (a specified opinion) :think
[no obj] :to regard the existence of God as a fact :to have religious beliefs
[no obj] :to have trust in the ability, worth, etc., of someone or something
informal - used for emphasis in phrases that express certainty, surprise, annoyance, etc.
believe in
[phrasal verb]
believe in (something)
to have faith or confidence in the existence of (something)
to have trust in the goodness or value of (something)
believe in (someone) :to have trust in the goodness or ability of (someone)
can't believe your eyes/ears
If you can't believe your eyes/ears or can hardly/scarcely believe your eyes/ears, you are very surprised at or upset by what you are seeing or hearing.
make believe
to act as though something that is not true or real is true or real :pretend
seeing is believing
The expression seeing is believing means that when you actually see something, you have to believe that it exists or is true.