Abarim Publications' online Biblical Greek Dictionary
The verb λανθανω (lanthano) means to escape notice, to be unseen, to be unknown about, but with a clear implication of being very much there but somehow hidden from direct sight or otherwise not noticed.
In later Greek texts (including the New Testament) this verb began to assume the meaning of forgetting something, that is: the slipping out of sight or awareness of something that was previously seen or known about, and which is still very much there. Both our verb and its amplified version επιλανθανω (epilanthano) occur in the curious urge to not "forget" hospitality because through it some folks "unknowingly" entertained angels. Contrary to common conception, this does not mean that the angels and the strangers are the same — angels may be entertained from observing people being kind to strangers. It also doesn't mean that a received stranger may secretly be an angel, so that the host doesn't know that he's entertaining an angel. The host knows when he's entertaining an angel, even when nobody else does (which is when the host's general hospitality is unseen by others).
Our verb λανθανω (lanthano) is obviously closely akin the verb μυω (muo), which means to cover and from which comes the word μυστηριον (musterion), meaning discovery or "mystery"; something that is hidden for most people but understood by folks in the know.
Our verb λανθανω (lanthano) is used a mere 6 times in the New Testament, see full concordance, but from it come the following important derivatives:
- Together with the particle of negation α (a): the adjective αληθης (alethes), literally meaning not-hidden or not-forgotten or even not-concealable and unforgettable, but generally translated with "true". This laden word has been oft discussed but it does not refer to some set of absolute statements that exist independently, but rather to human convention: that which is agreed upon by everybody — and remember that in the natural societies of Biblical times, an error in judgment could easily lead to death, destruction, disease, invasions and revolts; back then, true and false were literally matters of life and death. The search for truth, therefore, is the quest for a system of expression in which everybody feels wholly safe, wholly free and wholly confirmed (John 5:31). Truth has to do with synchronization, which in turn allowed man to develop speech, script, science and ultimately the New Jerusalem. See for a broader discussion of these things our article on the noun αγαπη (agape). Our adjective αληθης (alethes) is used a mere 25 times, see full concordance, but from it in turn derive:
- The noun αληθεια (aletheia), meaning truth, or rather (as indicated above): convention, agreement and synchronization. Jesus personified truth (John 14:6), which is the reason why ultimately all knees will bow and all flesh will see him together (Isaiah 40:5). Truth is that which cannot be hidden, and is the only thing that everybody can agree on. It has nothing at all to do with any religion. Our noun is used 110 times; see full concordance.
- The verb αληθευω (aletheuo), meaning to pursue convention or agreement. It's used only twice in the New Testament, namely in Galatians 4:16 and Ephesians 4:15, and in the latter occurrence it's linked directly to αγαπη (agape), which describes a similar process, as noted above.
- The adjective αληθινος (alethinos), meaning pertaining to or in pursuit of convention and synchronization: something about which there is no disagreement or about which there will be no disagreement when all that can be unearthed is unearthed. Something that will never fail, never go away and has always been part of the eternal order of creation. This word is often translated with true or genuine, but it should be noted that this word describes something that is part of the physical universe, not something that exist in some moral code, cultural expression or even the best intentions or sincerest beliefs of humans. This adjective is used 27 times; see full concordance.
- The adverb αληθως (alethos), meaning in the way of the unforgettable and the perpetual. This word is commonly translated with truly. It occurs 21 times; see full concordance.
- Together with the preposition εκ (ek), meaning out or from: the verb εκλανθανω (eklanthano), also meaning to hide or forget but with an emphasis on extraction and removal from that which is noticed. This verb occurs only once, in Hebrews 12:5, where it appears in the passive voice. In the classics this passive form is used to mean to forget utterly (instead of to be forgotten).
- Together with the preposition επι (epi), meaning on or upon: the verb επιλανθανω (epilanthano), meaning to (cause to) forget, with an implied emphasis on burial and covering over. This verb occurs 8 times, see full concordance, and from it in turn derives:
- The noun επιλησμονη (epilesmone), meaning forgetfulness (James 1:25 only).
- The adverb λαθρα (lathra), meaning covertly, secretly. This adverb is used 4 times; see full concordance.
- The noun ληθη (lethe), meaning oblivion (2 Peter 1:9 only). From this noun come our English words lethal and lethargy, and Lethe is also the name of one of five rivers of Hades; one that caused forgetfulness in all who drank from it.