In linguistics, specifically phonetics and phonology, schwa (sometimes spelled shwa) refers to the mid-central vowel sound (rounded or unrounded) in the middle of the vowel chart, denoted by the IPA symbol ə, or another vowel sound close to that position. An example in English is the vowel sound in the second syllable of the word sofa. Schwa in English is limited to unstressed positions, but in some other languages it can occur as a stressed vowel.
In relation to certain languages, the name "schwa" and the symbol ə may be used for some other unstressed and toneless neutral vowel, not necessarily mid-central.
Read more about Schwa: Etymology, Description, Indonesian and Malay, Schwa Indogermanicum, Further Reading