In phonetics, apheresis (/əˈfɛrᵻsɪs, əˈfɪərᵻsɪs/; British English: aphaeresis) is the loss of one or more sounds from the beginning of a word, especially the loss of an unstressed vowel, thus producing a new form called an aphetism (/ˈæfɪtɪzəm/).
Apheresis comes from Greek ἀφαίρεσις from ἀπό apo, "away" and αἱρέω haireo, "to take."
In historical phonetics, the term "apheresis" is often but not always limited to the loss of an unstressed vowel. The Oxford English Dictionary gives this particular kind of apheresis the name aphesis (/ˈæfᵻsɪs/; from Greek ἄφεσις).