noun
General word for a handheld umbrella or parasol used against rain or sun.
雨が降りそうだから傘を持って行こう。
It looks like rain, so let's take an umbrella.
日差しが強いので日傘をさした。
The sun was strong, so I put up a parasol.
noun
umbrella-shaped thing; lamp shade; mushroom cap
Used for things that resemble an umbrella in shape, such as a lamp shade or the cap of a mushroom. The technical term for mushroom cap is pileus.
See also: 笠
ランプの傘が少し傾いている。
The lamp shade is slightly tilted.
このキノコの傘はとても大きい。
The cap of this mushroom is very large.
笠 refers specifically to a traditional conical hat, while 傘 is the general word for umbrella and umbrella-shaped objects.
The kanji 傘 is a pictograph of an umbrella. The word かさ is native Japanese and its origin is uncertain.