metaplasm

from The Century Dictionary.

• noun In grammar: A change or transmutation in a word by adding, transposing, or retrenching a syllable or letter.
• noun Formation of an oblique case or cases from a stem other than that of the nominative.
• noun In botany, protoplasm containing certain carbohydrates which are eventually separated from it in the formation of cell-walls or as secretions.
• noun In cytology, a collective term applied to lifeless or non-living substances or inclusions such as yolk-bodies, starch, pigment, etc., in the cell-protoplasm, as distinguished from the living substances.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Gram.) A change in the letters or syllables of a word.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun linguistics Any change in a word made by altering its letters or sounds
• noun biology A small particle (often nutrient) within a cell