Physical:
* Not thick or wide: This is the most common meaning. For example, "a thin slice of bread," "thin hair," "a thin book."
* Lacking in weight or substance: This can describe a person's body, but also things like "thin soup" (not thick or creamy) or "a thin argument" (lacking in solid points).
* Not dense or concentrated: For example, "thin air" (not dense), "a thin crowd" (not many people).
Figurative:
* Lacking in detail or substance: This applies to descriptions, arguments, or stories that are shallow or unconvincing. For example, "a thin excuse," "a thin plot."
* Fragile or easily broken: For example, "a thin ice," "a thin layer of paint."
To make thinner:
* To reduce the thickness or density of something: For example, "to thin the paint," "to thin the soup."
The best way to understand the meaning of "thin" is to consider the context in which it is used.