What does brother mean?
A brother is most fundamentally a male sibling — a boy or man who shares at least one parent with another person. Beyond this core familial sense, the word extends to any man bound to others by shared membership or purpose: monks are addressed as "Brother," trade-union members call one another brothers, and soldiers speak of brothers-in-arms. It also serves figuratively to express solidarity or kinship between men who share no blood tie, as in "a brother in need." The word carries warm connotations of loyalty, protection, and belonging, though it can be used ironically or as an expression of mild dismay. Derivatives such as brotherhood, brotherly, and brethren extend its reach into language about community and affection. Few English words are as old or as widely cognate across related languages.
A male sibling; a boy or man sharing one or both parents with another person.
"He looks up to his older brother."
Distinguished by birth order as elder/older brother, younger/little brother, or twin brother.
A male member of a religious order, fraternity, union, or similar community, often used as a title.
"The brothers of the abbey gather for prayer at dawn."
Capitalized when used as a formal title, e.g., Brother John.
A close male friend or ally; used figuratively to express solidarity between men.
"He treated every soldier in his unit as a brother."
The regular plural is "brothers." The archaic or religious collective "brethren" persists chiefly in church and formal communal contexts.
"The two brothers opened a bakery together."
"Brother" traces back to an Indo-European root so ancient that Sanskrit, Latin, Greek, and English all still carry its echo in words like bhrātā, frater, phrātēr, and brother itself.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of brother
The word brother descends directly from Old English brōþor, which in turn comes from Proto-Germanic *brōþēr. Its lineage reaches further still to the Proto-Indo-European root *bʰréh₂tēr, making it a genuine cognate of Sanskrit bhrātā, Latin frater, Greek phrātēr, and Irish bráthair — one of a small set of kinship terms preserved across the Indo-European family for thousands of years. The Latin branch of the same root gives us fraternal, fraternity, and friar.
Related word forms
How brother is actually used
In formal religious contexts, "Brother" functions as a courtesy title before a name. In informal American English, "brother" can serve as an exclamation of exasperation ("Oh, brother!") or as casual address ("bro"). The collective plural "brethren" survives mainly in religious or archaic registers.
Easily confused with brother
"Bother" is a verb meaning to annoy or trouble someone, while "brother" is a noun meaning a male sibling.