A weed is a wild plant growing where it is not wanted, especially among cultivated plants, while an herb is a plant deliberately grown to flavour food or used in traditional medicine. The difference is really about intent: dandelions on a lawn are weeds because nobody planted them there, while basil in the same garden is an herb because it was planted on purpose. One gardener's weed can even be another's herb, depending on whether it was welcome.
The core difference
Weed describes an unwanted plant growing where it should not, while herb describes a plant grown on purpose for flavouring or medicine.
- weed — a wild plant growing where it is not wanted, especially among cultivated ones: dandelions are a common weed on suburban lawns.
- herb — a plant used to flavour food, especially the leaves: she sprinkled fresh herbs like basil and thyme over the pasta.
How to tell them apart
The clearest test is purpose: an herb is planted and tended for a reason, whether that is seasoning a dish or making a medicinal tea, while a weed simply turns up uninvited and competes with the plants a gardener actually wants. The same plant, such as mint, can even be a prized herb in one garden and an unstoppable weed in another if it spreads where it should not.
Weed is also a verb, meaning to pull unwanted plants out of a garden or field, as when someone spends the morning weeding the vegetable patch. Informally, weed is slang for marijuana too, a sense that has nothing to do with gardening.
