Comments: PAT *mǝca (cf. also Bzyb. á-mca). PAK *mac̣ʷá. Ub. def. á-mǯ́a. The root presents some irregularities. The PAT and Ub. forms reveal a secondary delabialisation (PAT *mǝca < *mǝcʷa; Lomtatidze (1942, 862, 865) is probably right in assuming that the original labialized form is preserved in PAT *macʷǝ-śǝ 'lightning' ("fire"+"beat"); Ub. mǝǯ́á < *mǝʒʷa). The same languages also have lost glottalisation. The most archaic form (judging from the external evidence) is PAK *mac̣ʷá.
Cf. also PAT *cʷǝ- in *cʷǝ-mǝsa 'tinder' ( = PL *c̣ojɨ-mäs, see under *mä̆sA); this is probably the only trace of the prefixless stem in WC languages.