Worthwhile means worth the time and effort it costs. A worthwhile project, well worthwhile, not worthwhile.
It is written as one word when it comes before a noun — a worthwhile cause — and either one word or two after a verb, though one word is now standard everywhere. Worth your while is the older phrase and is still used: make it worth your while. Note that worthwhile weighs cost against benefit, so calling something worthwhile is a judgement about the price as well as the value.
1adjectiveworthwhileWorth the time and effort it costs.
“Volunteering at the shelter is hard work, but it feels worthwhile.”
worthwhile is a quality of being worth the cost.
The phrase worth one's while means worth the time spent — while here is the old noun meaning a period of time, the same while as in a long while. The compound closed up in the nineteenth century.
From worth + while.
Etymology from Wiktionary, CC BY-SA