I generally use a for each type loop or a map because I am usually applying some function across a collection, and in both cases I use the singular name from the collections plural.

’Cities.map(city -> …)’

For (val city in cities)

If I actually need the index for some reason I still prefer loop structures that give me the index and the item together

*note syntax pulled out of my head and not necessarily belonging to any specific language.

For ( city, index in cities)

cities.map((city, index) -> … )

If I need to double loop a matrix array I would use rowIndex and ColIndex for the indexes.