a male with the same parents as someone else
"my brother still lives with our parents"
a male person who is a fellow member (of a fraternity or religion or other group)
"none of his brothers would betray him"
(Roman Catholic Church) a title given to a monk and used as form of address
"a Benedictine Brother"
Son of the same parents as another person.
"The new Brother Thomas greeted us warmly as he walked down the hallway in his habit."
Title of respect for an adult male member of a religious or fraternal order.
In plain English: A brother is a male sibling who shares at least one parent with you.
"My brother and I went to the park yesterday."
Usage: Use "brother" to refer to a male sibling or a close male friend in informal conversation. Avoid using it as a title of respect for a religious member unless you are specifically addressing someone within that order or quoting formal language.
To treat as a brother.
"After saving me from that dangerous situation, he truly became my brother."
In plain English: To brother means to join two pieces of wood together using bolts and nuts.
"The older brother helped his younger sibling tie his shoes before school."
Usage: The verb form of "brother" means to regard someone as a sibling or close friend, but it is rarely used in modern English and often sounds archaic or overly formal. Most speakers simply use phrases like "treat as family" or "consider a friend" instead of saying they "brothered" with someone.
Expressing exasperation.
"Brother, I can't believe you forgot to buy milk again!"
The word "brother" traveled into English from Old English brōþor, which itself came from the same root used in other Germanic languages. Its meaning has remained consistent since its origins in Proto-Indo-European, where it simply referred to a male sibling.