Words for "mother" begin with the letter M in many languages, but not all of them. The reason has to do with the physiology of infant vocalization. Among the first sounds babies make are bilabial sounds with an open vowel, the lips coming together to form a B or M sound. In some East Indian languages, for example, the word for "father" is Baba. The sounds of nursing involve a nasalized, or N sound. Then parents interpret these sounds and give them meaning, often deciding that these sounds designate adults involved. Beyond the physiological factors, that initial M also reflects the fact that Indo-European languages share common linguistic roots, as is the case with madre in Spanish and mère in French, both of which are cognate with English mother. This is part of a complete episode.