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mid-15c., "concealed, secret," from Latin latentem (nominative latens) "lying hid, secret, unknown," present participle of latere "to lie hidden," from PIE *laidh-, from root *la- "to be hidden" (cf. Greek lethe "forgetfulness, oblivion," Old Church Slavonic lajati "to lie in wait for"). Meaning "dormant" is from 1680s.
latent la·tent (lāt'nt)
Present or potential but not evident or active.
In a dormant or hidden stage, as an infection.
Undeveloped but capable of normal growth under the proper conditions.
Present in the unconscious mind but not consciously expressed.