Given this, some suggest that weakened may have been a separate phoneme in PS.

They are used to demonstrate that two phones constitute two separate phonemes in the language.

But because they have so little in common in phonetic terms they are still considered separate phonemes.

The hard and the palatalized consonants are considered separate phonemes in Bulgarian.

The stops are not confirmed to exist as separate phonemes in any language.

The glottal stop is not a separate phoneme.

Researchers differ in whether the paired palatalized consonants should be analyzed as separate phonemes.

Therefore it is not considered a separate phoneme in Proto-Dravidian.

Later, this develops into a separate phoneme; see below.

Long vowels may or may not be separate phonemes.