Frail adjective - Easily broken.
Usage example: a frail eggshell
Weak is a synonym for frail in feeble topic. In some cases you can use "Weak" instead an adjective "Frail", when it comes to topics like characteristic, quality, strong, flimsy. popular alternative
Weak adjective - Lacking bodily strength.
Usage example: the little boy was simply too weak to lift the box
Frail is a synonym for weak in quality topic. You can use "Frail" instead the word "Weak" as an adjective or a noun, if it concerns topics such as strong, feeble, unhealthy, thin and weak. popular alternative
Both words in one sentence
- The victim is sufficiently frail and weak that his death is not unexpected in any case, and is too feeble to put up a significant struggle.
Source: Vorpal Pillow
- He's always depicted as frail and weak, but just how frail and how weak depends on whatever makes the joke work.
Source: Strong as They Need to Be
- If the hero is strong and invulnerable, Mission Control is weak and frail.
Source: Mission Control
Google Ngram Viewer shows how "frail" and "weak" have occurred on timeline