Tenuis \Ten"u*is\, n.; pl. {Tenues}. [NL., fr. L. tenuis fine,
thin. See {Tenuous}.] (Gr. Gram.)
One of the three surd mutes [kappa], [pi], [tau]; -- so
called in relation to their respective middle letters, or
medials, [gamma], [beta], [delta], and their aspirates,
[chi], [phi], [theta]. The term is also applied to the
corresponding letters and articulate elements in other
languages.
[1913 Webster]