Similarity (n.) striking us need not come before we use the same word; the striking may consist, partly or wholly, in our being prompted to use the same picture or phrase.
Similarity (n.) is not explained by a common element; saying two strains 'have something in common' is only another way of saying they are similar.
Similarity (n.) as a feeling is hard to locate: the comparing is a complicated activity, and the feeling may have been only the word similar suggesting itself.
Similarity (n.) depends on the case: a bluish green is like a yellowish green in some uses and most unlike it in others.
Similarity (n.) one sees but cannot describe is itself the experience: 'I do see a certain likeness, only I can't describe it' is what characterizes it.
Similarity (n.) is noticed rather than seen — one cannot see a likeness between two faces from one stroke of the hour to the next.
Similarity (n.) is internal when shapes like circle and parabola resemble each other, external when two people happen to look alike now.