تَسَاهُلٌ

is synonym with تَسَامُحٌ. (S, K.) You say تساهلوا meaning They acted in an easy, or a facile, manner, one with another; (MA, TA in article يسر;) or gently; synonym تَيَاسَرُوا. (TA in that article)

See also 3.

[In the present day it is used as meaning The being negligent, or careless, فِى أَمْرٍ in an affair.]

[As a conventional term in lexicology, or in relation to language, it means A careless mode of expression occasioning] a deficiency in the language of a [writer or] speaker without reliance upon the understanding of [the reader or] the person addressed: (KT: [in one of my copies of that work, this explanation is omitted in the text, but written in the margin; and it is there added that it is what commonly obtains:]) or it means [sometimes such a mode of expression] that a phrase is not correct if held to be used according to the proper meaning, but is correct if held to be used according to a tropical meaning: or the mention of the whole when meaning a particle (Marginal notes in the copy of the KT above mentioned.) [See also تَسَامُحٌ, for which it is often used.]