weak spot
Word family
Synonym discussion
Sense: noun/1
All four words describe some form of lack of strength, but they differ in specificity and register. 'Weakness' is the broadest — it can refer to a character flaw ('Greed is his weakness'), a physical frailty, or a lack of skill. 'Weak spot' is more concrete and localised: it points to a specific place, person, or area where something is vulnerable. 'Vulnerability' is more formal and often used in technical or psychological contexts, focusing on the capacity to be harmed. 'Achilles heel' is an idiom from Greek mythology that describes a single fatal weakness in an otherwise strong person or system — it carries a more dramatic tone. For example, while you might say 'maths is my weak spot' to describe an academic difficulty, calling it your 'Achilles heel' would imply it is your most critical, possibly career-limiting deficiency.
Common collocations
Etymology
The compound noun 'weak spot' combines the Old English-derived adjective 'weak' (from Old Norse 'veikr', meaning pliable or lacking strength) with the Old English noun 'spot' (meaning a mark or small area). The phrase appears in English from at least the 16th century, initially describing physical points of weakness in materials or structures. By the 19th century, it had acquired the figurative meaning of a personal vulnerability or character flaw.