Etymologically, and in mainstream English the word means "feeling" but is rare and now archaic.[From Poul Anderson's `Polesotechnic League' stories, going back at least to 1963]An evolved biological intelligence.Implies human-level cognitive and linguistic ability but not necessarily tool use.We can not only communicate, Trade, and fight, but form joint business ventures, cheat each other at cards, and even fall in love.Indeed, Aliens with Forehead Ridges raise a profound question in evolutionary biology.However, Aliens with Forehead Ridges continue to thrive in Hollywood Scifi. In casual encounters with the material universe, we rarely feel any difficulty here, since we usually deal with things that are clearly alive, such as a dog or a rattlesnake; or with things that are clearly nonalive, such as a brick or a typewriter.
In general, Aliens fall into two distinct groups, REALLY ALIENS and ALIENS WITH FOREHEAD RIDGES.1) Really Aliens are truly unearthly. The occasional intelligent bear or radish may also appear, or practically anything else.
It would be expecting much of anyone to guess that an oyster were alive if he came across one (for the first time) with a closed shell.
Could a glance at a clump of trees in midwinter, when all are standing leafless, easily distinguish those which are alive and will bear leaves in the spring from those which are dead and will not?
Convergent evolution might well produce a generally humanoid body plan, just as sharks and dolphins have a similar overall configuration.
But Aliens with Forehead Ridges have much more than a general similarity to Earth Humans.