When is a thought considered a lustful thought?

[TonyChanYT]

Berean Study Bible James 1:

15 Then after desire has conceived, it gives birth to sin; and sin, when it is full-grown, gives birth to death.

desire
ἐπιθυμία (epithymia)
Noun - Nominative Feminine Singular
Strong's 1939: Desire, eagerness for, inordinate desire, lust. From epithumeo; a longing.

Matthew 5:

28 But I tell you that anyone who looks at a woman to lust after her has already committed adultery with her in his heart.

lust after
ἐπιθυμῆσαι (epithymēsai)
Verb - Aorist Infinitive Active
Strong's 1937: To long for, covet, lust after, set the heart upon. From epi and thumos; to set the heart upon, i.e. Long for.

These are two different but related Greek words. Looking at something is okay but looking at something to lust after or covet it is not okay. The Pharisees focused on external behaviors but Jesus shifted the focus inwardly to the heart. Your conscience will tell you whether you have sinned or not.

Lust is not just sexual. Acts 20:

33 I have not coveted [G1937] anyone’s silver or gold or clothing.

The same Greek word can mean also "covet'.

 

[Lambano]

The same Greek word can mean also "covet'.

An ex-Buddhist I met on another forum would've said, "crave".

Building on the "covet" theme, is it when a man desires to "possess" a woman sexually? Is it the craving to possess more?

Hey, Jesus, how come You never mentioned women lusting for men?

 

[TonyChanYT]

Building on the "covet" theme, is it when a man desires to "possess" a woman sexually?

Right

Is it the craving to possess more?

That's good imagery