di-, dicho-, dich-

(Greek: number two; twice, divided, double; unalike; a number used as a prefix)

Having only two digits; such as, being two-toed.
Having two digits on each limb.
One who marries a second time; especially, after the death of the first spouse.
A letter occurring in certain early forms of Greek and transliterated in English as "w".

From Latin, which came from Greek di-, "two" + gamma, "gamma" (because its shape resembles two gammas).

digastric (adjective), more digastric, most digastric
Pertaining to two small muscles located under the jaw: The term digastric muscles refer to these specific muscles which assist in lowering each of the upper and lower bony structures in vertebrates that form the framework of the mouth and containing the teeth.
diglossia (s) (noun), diglossias (pl)
1. A situation in which a language exists in two forms, one formal or literary and the other informal, and a person uses the form which is appropriate for a particular situation.
2. The existence of a formal literary form of a language, considered more prestigious, along with a colloquial form used by most speakers and considered to be a lower status.
3. A sociolinguistic phenomenon in which complementary social functions are distributed between a prestigious or formal variety and a common or colloquial variety of a language; such as, in Greek, Tamil, or Scottish English.
4. In medicine, a form of schistoglossia in which the lateral lingual swellings fail to fuse, producing a bifid tongue or one with a lengthwise cleft.
diglossus (s) (noun), diglosses (pl)
An individual showing a bifid tongue or one that is divided longitudinally or lengthwise.
A bilingual inscription, book, edition, or person.
1. A sequence of two adjacent letters or symbols.
2. Two signs or characters combined to express a single articulated sound; such as, ea in "head", or th in "bath".