What is the meaning of Prothesis?

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

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

Credence table.

Source: wiktionary.org