"The child has small black pants."
Translation:L'enfant a un petit pantalon noir.
No, you cannot expect to translate word for word from one language to another. In English we could say “The child has a pair of small black pants.”, because the French “un pantalon” equals “a pair of pants”, but we often just say “pants” even for one pair of pants or trousers for the British. We cannot say “a pants” in English.