Arabic uses markers such as the comparative kāf (كـ) in “Zayd is like a lion” and kaʾanna (كأنّ) in “It is as though Zayd were a lion.” English “like” and “as if” perform comparable functions.
A simile can remain intelligible without an overt comparison marker. Under the right context, “Zayd is a lion” may function as a condensed resemblance in courage while both terms remain in the utterance.
Not every unmarked expression has the same technical classification. One must consider whether the compared terms are present, whether context blocks a literal reading, and how the expression is grammatically constructed.