Abarim Publications' online Biblical Greek Dictionary
The familiar adjective ισος (isos) means alike or equal, and is the source of the many "iso-" words in English (isobar, isograph), whose second part is usually Greek. They also often come with a Latin equivalent (or isodynamic, if you will), which starts with the Latin equivalent "equi-" and is followed by a Latin verb. Neither the Greek nor the Latin have an clear etymology but appear related to words meaning flat or level.
Specifically, our adjective ισος (isos) predominantly describes alignment in countable and measurable qualities, whereas the somewhat similar adjective ομοιος (homoios) specializes in alignment or lateral correspondence of abstract and uncountable qualities.
Our adjective used 8 times in the New Testament, see full concordance, and from it derive:
- Together with the complicated word αγγελος (aggelos), angel or messenger: the adjective ισαγγελος (isaggelos), which doesn't simply mean angel-like or angelic but rather having the same defining (and measurable) qualities as an angel (Luke 20:36 only).
- The noun ισοτης (isotes), meaning (measurable) equality (2 Corinthians 8:13, 8:14 and Colossians 4:1 only).
- Together with the noun τιμη (time), worth, dearness or honor: the adjective ισοτιμος (isotimos), meaning of equal honor or equal value (2 Peter 1:1 only).
- Together with the verb ψυχω (psucho), to breathe, to need, to want: the adjective ισοψυχος (isopsuchos), meaning like-minded, or of the same motivation (Philippians 2:20 only).
- The adverb ισως (isos), literally meaning equally, but in the classics often deployed to describe a suggested equality or high probability: likely, probably. This adverb occurs in Luke 20:13 only, where the lord of the vineyard decides to send his son, as the workers will "probably" recognize him as his heir.