believe is an English word, a verb that means believe.
believe, or I believe (in English) is to have confidence in the existence or truth of something, even though there is no absolute proof of that belief. Ex: I believe in God. / I believe in god (that God exists).
The word believe it can also be used to indicate belief or disbelief in something a person says. Ex: I don't believe you because you lie to me all the time. / I don't believe you because you lie to me all the time.
Furthermore, believe it can also be a word related to the act of assuming, understanding or supposing something. Ex: My mother is not home, I believe she went to my aunt's place. / My mother is not at home, I believe she is at my aunt's house.
There are several known expressions with the word believe. believe in yourself means "believe in yourself" and is an expression used to motivate, encouraging the person to believe in their abilities. Ex: Don't listen to what they say, you just have to believe in yourself / Don't listen to what they say, you just have to believe in yourself.
Another common expression is "believe in me"which means "believe me". Ex: Believe me when I say I love you / Believe me when I say I love you. Believe in me is also a song by singer Demi Lovato.
In the field of music, singer Cher released a song called "Believe" in 1998. Later in 2012, Justin Bieber released an album called Believe, which contained a song called Believe. The same artist released in 2013 a documentary called "Justin Bieber's Believe".