ἐπιθυμῆσαι [5 verses](aor inf act) "To lust after" is epithymeo, which means "to set one's heart upon", "to desire", "to covet," and "to long for." The root of this word is thymos, (θυμός), which is the seat of passion and heat. The prefix means "upon." -- (WW) "Lust" is a Greek verb that means "to set one's heart upon", "to desire", "to covet," and "too long for." The verb indicates heat and passion, but not sexual passion (see this article about the Greek root of this word meaning "chest") Jesus uses this word five times, always in reference to hunger and thirst except for here. The form is an infinitive uses as a noun describing the action, so "the craving."