みa quality you feel or taste
On some adjectives, み takes the place of the final い and makes a noun for a quality you feel or taste: 甘い is "sweet", and 甘み is the sweetness you taste in something.
This soup has the sweetness of the vegetables in it.
The warmth of the wood comes through in this furniture.
How to form it
甘い → 甘み
Only some adjectives take it. The result is a noun, most often with がある (it has it), が出る (it comes out) or を感じる (you feel it).
Words you'll meet
Mostly tastes, what the body feels, weight and depth, and emotions. All are everyday words.
痛みpain
The pain is still there, but it is better than yesterday.
楽しみsomething to look forward to
I'm looking forward to summer vacation.
悲しみsadness, grief
The grief of losing a friend doesn't fade easily.
深みdepth
Over the years, his acting has gained depth.
強みa strength, a strong point
This area's strength lies in its convenient transportation.
弱み is a weak point.
み or さ?
These adjectives take さ as well. さ gives a measurement, or how much. み gives the quality as you feel it.
This box weighs two kilograms.
A measurement: what the scales say.
Even his few words carried weight.
The weight you feel in his words.
This board is three centimeters thick, and when you pick it up you can feel how thick the wood is.
厚さ is the number. 厚み is what your hand feels.
楽しさ is how much fun something is; 楽しみ is something you look forward to.
Only some adjectives
There is no 暑み, 広み or 大きみ.
Not said: 今年の
(The heat this summer is terrible.)
暑さ.
Close neighbours
さN4
Goes on nearly any adjective, so it is the safe one when you make the noun yourself: 暑さ, 大きさ, 高さ.
I can't take the heat.
Check yourself
1"Please weigh this parcel."
この
Choose an answer to see why.
2"I was surprised at how big the room was."
部屋の
Choose an answer to see why.
More detail
The み of a taste is often written 味, still read み: 苦味, 旨味.
高み is a high place, not height: 高みを目指す, to aim high.
More sentences
This soup leaves a faint bitterness in the aftertaste.
This fabric takes on a reddish tinge in the light.