The schwa is the unwritten “uh” sound that is basically every unstressed vowel, and is written as an upside down e. The schwa is the first syllable in amazing (ǝ-MA-zing). The schwa is the second syllable in replicate (RE-plǝ-cate). The schwa is the first syllable in syringe (sǝ-RINGE). Because it’s unwritten and only noticeable when hearing the actual word, the schwa is also notorious in making English hard to learn. (Not to mention our bad habit of deleting or adding schwas at any given notice, such as “camra” instead of camera or “nuculer” instead of nuclear.)
The schwa, which is a German translation of the Hebrew “schva,” (the vowel written under letters to indicate an “eh” sound), was first used by Johann Schmeller who invented the upside down e notation in his 1821 grammar of Bavarian German. He invented this symbol to show the difference in dialects, which are often dictated by the difference in unwritten stresses (mainly schwas).
Because English is such a stress-timed language, schwas are one of the biggest unspoken factors in our language. When talking, we base our rhythm on timing the space between stressed syllables in our words. If we speed up, we speed up the distance between the stressed groups of our words. This quickening naturally forces us to sacrifice the schwa, since its unstressed nature is the rubber gasket in the pressure valve and is most flexible. When slowing down or stressing something, we lengthen the schwa, or add ones in, such as saying “caraaazy” instead of crazy. When a group of people habitually add, stress, slow, or speed the schwa, that’s when dialects are formed.