"Plates are on the table"
Translation:Sahani zipo juu ya meza
Both definite and indefinite articles should be accepted, as there is nothing to indicate which should be used. Therefore all combinations should be accepted: [The plates / Plates] are on [a table / the table(s)]. If you find sentences where either the definite or indefinite article is not accepted, please report it.
Oh sorry, now I see what you're asking. Yes, the use of -po indicates a specific location (so on second thought, "the" table is probably best). But without further context, this still doesn't give any reason to favor "the plates" over just "plates." If you had already referred to specific "blue" plates or whatever, then yes, "the plates" would be the better translation. But if you are simply saying there are plates available on the table, then no article is fine. But this is getting awfully pedantic. :)
Even so it could be several specific tables. Being a definite location does not imply that it has to be singular.
However that being said for the table(s)...
Bad news concerning the plates. They are indef/def but absolutely plural. The zi in zipo indicates that sahani in this sentence is plural.
If you want one plate the sentence would be:
Sahani ipo juu ya meza.