antennas-antannae
British plural its self is larvas
Symposiums already is a (British??) plural of Symposium. The other accepted plural form is symposia.
The correct plural form of criterion is criteria.
The plural of harbor is harbors. In British English the singular is harbour and the plural is harbours.
The plural of odour is odours. As in "there are strange odours coming from the room".
Natural in Italian is naturale (singular) or naturali (plural).
"Flavored" is a verb; the noun form is "flavor", for which the plural is "flavors." (British spelling: flavoured, flavour, flavours)
It is mangoes in British English.
Natural is an adjective so cannot have a plural form. It is from the noun nature, for which the plural is nature, that is, encompassing all of nature.
A few natural resources of British Columbia: Forestry; mining; natural gas (tar sands.)
The plural of "meter" is "meters." In British English, it can also be spelled as "metre," with the plural being "metres." Both forms refer to the unit of measurement for length in the metric system.
British English it is tyres. American English it is tires.