This discussion happens all the time on comp.dsp, between primarily
computer-science folks approaching DSP and EE types approaching it.

EE folks' definition of "linear" implicitly includes time invariance; DSP
people have to see it stated explicitly (as "LTI": Linear Time Invariant) lest
they think "linear" just means having no second-or-higher-order terms.

It is not a deficiency on either party's part, just a difference of definition
in each's respective discipline (is that enough alliteration?).

Therefore, I advise each to bend this much: Use the full phrase "Linear
Time-Invariant" when this miscommunication is suspected, so both know what the
hell the other is talking about. Now go and sin no more.

--
Weav
NW6E and other vices