a kid: a young male goat, still young enough to be at its mother's milk
The word names the ordinary young male goat, the small animal of everyday household life. Hebrew keeps a precise vocabulary for goats: the general word covering goats of any age or sex is עֵז, the mature shaggy male is שָׂעִיר, and the full-grown buck is תַּיִשׁ. A kid sits at the young end of that range, and it turns up most often in the fixed phrase "kid of the goats," which simply pins down the species.
Because a kid feeds a small group at a single meal and costs little, it became the natural gift and unit of exchange in Israel's stories. It is the meal set before a divine visitor (Gideon and Manoah each prepare one), the promised payment Judah sends to Tamar, the tribute a father sends to the king, and the offering a pilgrim carries to the shrine. Its small size also made it a picture of helplessness: Samson tears a lion apart "as one tears a kid," and Isaiah's vision of peace lays the leopard down beside the kid, the classic easy prey now safe.
The same little animal stands at the center of one of the Bible's most argued laws, the command not to boil a kid in its mother's milk (Exodus 23:19; 34:26; Deuteronomy 14:21). The argument is about what the law means, not about what the word means: in all three verses the word is simply the young goat. Its female counterpart, the she-kid (transliterated "gediyyah"), appears just once, in Song of Songs 1:8.