/ə/

The schwa is an unstressed centra vowel and is the most common vowel to appear in English. There is no similar sound in Spanish. We tend to assimilate is to an unstressed "e" when it is not final

Most important spelling

It has no regular character to represent it. Any voquel or group of vowels may in unstressed position may respresent /ə/.

Minimal Pairs.

As it never occurs in stressed position, there are no contrastive elements.