Definition of "prothesis"

(phonology) The prepending of phonemes at the beginning of a word without changing its morphological structure, as in Spanish esfera from Latin sphaera (“sphere”) (without prothesis the word would have become *sfera).

(Christianity) The preparation and preliminary oblation of the Eucharistic bread and wine in the Divine Liturgy of the Eastern Orthodox and Eastern Catholic Churches.  examples

(by extension) Credence table.  examples