Luke 21:20 And when ye shall see Jerusalem compassed with armies, then know that the desolation thereof is nigh.
When, however, you might see encircled by camps, Jerusalem, then you might know that it has come near, that desolation of it.
Though this verse is very different than Matthew 24:15 and Mark 13:14 which mention the "abomination of desolution", but it seems based on it since they all share a word used nowhere else. However, it adds a couple of words that are unique for Jesus.
The Greek word translated as "and" means "but", "however", and "on the other hand". Since it always falls in the second position, translating it as "however" often captures its feeling better.
The Greek word translated as "when" introduces a phrase that explains a certain condition so "whenever" or "since."
The verb translated as "ye shall see" means "to see" but it is used like we use the word "see" to mean "to know" or "to perceive." This verb is not the future tense, but in the form of possibility that indicates something that could happen at any time.
The word "Jerusalem" denotes the city or its inhabitants. Two different forms of this word appear in the NT. This version is used most heavily in Luke, mostly in his narration, but a few times in Christ's words. It seems to be the more formally Greek version of the name.
"Compassed" is from a verb used only where that means to "encircle" or "surround". It is in the form of an adjective.
The word translated as "with" primarily means "by", "under," or "with" (with the genitive and a passive verb). Its primary meaning is "under" both in the sense of moving under, being under, and being under different forms of compulsion.
"Armies" is another unique word that means "camp", and "encampment".
The Greek word for "then" means "at this time" or "then".
"Know" is a verb that means "to know", "to recognize", "make known", "to know carnally," and "to learn.
The word translated as "that" introduces a statement of fact or cause.
"The desolation" is from a Greek word that means "making desolate," the idea of being stripped bare" and being abandoned or deserted. It is in the possessive form. It too is from the Septuagint, but it appears elsewhere in Greek literature. Here, the Hebrew source word means "to be desolate", "to be deflowered," "to stun", "to be appalled", "to devastate", "to ravage", "to cause horror," and "to cause oneself ruin." When Christ refers to the "desert" or "wilderness" he uses the noun form of this word. This word is used only three times in the Gospels usually referring to a verse in Daniel.
The word translated as "thereof " is the Greek word commonly translated as third-person pronouns in English. The word means "the same" when used as an adjective. In the adverbial form, it means "just here" or "exactly there."
The word translated as "is nigh" is the verb form of an adverb "near" in space, time, and relationships. In English, we would say "nears" or, in the form here, "has neared," doesn't quite work so perhaps "has gotten close" or, in the case of time, "is nearly here."
Ὅταν (adv/conj) "When" is from hotan, which means "whenever (as a condition)," and "since (as a cause)." --
δὲ (conj/adv) "But" is de which means "but" and "on the other hand." It is the particle that joins sentences in an adversarial way but can also be a weak connective ("and") and explanation of cause ("so") and a condition ("if").
ἴδητε ( verb 2nd pl aor subj act ) "Ye shall see" is eido which means "to see", "to examine", "to perceive", "to behold", "to know how to do", "to see with the mind's eye," and "to know." --
κυκλουμένην [unique](part sg pres mp fem acc) "Compassed" is kykloō, which means to "encircle" or "surround"
ὑπὸ (prep) "With" is hypo (hupo), which means [with genitive] "from under (of motion)", "down under," under, beneath," indicating a cause with passive verbs, "by", "under," or "with", "under the cover or protection of", "of the agency of feelings, passions," "expressing subjection or dependence," "subordinate", "subject to;" [with accusative] "towards" and "under" (to express motion), "under" (without a sense of motion), "subjection", "control", "dependence," of Time, "in the course of", "during", "about," as an adverb, "under", "below," beneath, the agency or influence under which a thing is done"by", "before,' and "under," (with genitive and passive verbs of cause).
στρατοπέδων [unique]( noun pl neut gen ) "Armies" is stratopedon, which means "camp", and "encampment".
Ἰερουσαλήμ, "Jerusalem" is from Ierousalēm, which is a form of word that denotes the city or its inhabitants. Two different forms, this form and Hierosolyma, in the NT. Luke uses this form.
τότε (adv) "Then" is tote, which means "at that time" and "then." --
γνῶτε ( verb 2nd pl aor subj act ) "Know," is ginosko which means "to learn to know", "to know by reflection or observation," and "to perceive." --
ὅτι (adv/conj) "That" is hoti, which introduces a statement of fact "with regard to the fact that", "seeing that," and acts as a causal adverb meaning "for what", "because", "since," and "wherefore."
ἤγγικεν ( (verb 3rd sg perf ind act) ) "Is nigh" is eggizo, which means "to bring near", "to join one things to another," to draw near," and "to approach." This word does not appear in the Perseus dictionary. It comes from an adverb ἐγγύς, keggus, which means 1) (of place) "near", "nigh", "at hand," 2) (of time) "nigh at hand" 3) (of numbers) "nearly", "almost", "coming near," and 4) (of relationship) "akin to." --
ἡ ἐρήμωσις [uncommon](noun sg fem nom) "Desolation" is erêmôsis, which means "making desolate." It is from erêmoô, which means "to strip bare", "desolate", "to lay waste", "to abandon", "to desert" "to bereave," and "to be left without." The Hebrew source is shamem, which means "to be desolate", "to stun", "to be appalled", "to devastate", "to ravage", "to cause horror," and "to cause oneself ruin." Christ uses the noun form, eremos, that is translated as "desert" or "wilderness."
αὐτῆς. (adj sg femgen) "Thereof" is autos, which means "the same," and the reflexive pronouns, "myself", "yourself", "himself", "herself", "itself," or the oblique case of the pronouns, "him", "her," and "it." It also means "one's true self," that is, "the soul" as opposed to the body and "of one's own accord." In the adverbial form, it means "just here" or "exactly there." --