gemination (phonetics)
Definition - The doubling of what was originally a single consonant sound, i.e. holding it for approximately twice its normal length.

This phenomenon doesn't occur within words in normal spoken English, but it does occur between consecutive words when the first word ends with the same consonant that begins the next, e.g. calm man and night train (vs. night rain).

Gemination in Arabic

Etymology -
The term derives from the Latin geminare, to double.

Oxford English Dictionary -
Its first citation is from 1875:
"The gemination of the letters is not expressed in writing."
(P. Le P. Renouf Egypt. Gram. 8 )

Please comment