米 is rice as a grain — the raw material, before it is cooked.
THE こめ / ごはん BOUNDARY:
The switch happens at the rice cooker. You buy, wash, store, and harvest 米; the moment it is cooked it becomes ご飯, and that is also the word on the table and on the menu. Asking for 米 at a restaurant would sound like asking for a bag of grain.
RICE VOCABULARY:
- 米: uncooked rice
- ご飯: cooked rice; by extension, a meal
- 稲: the rice plant growing in the field
- 玄米: brown rice
- 白米: white (polished) rice
- 新米: the year's new crop — and, figuratively, a novice
READING NOTE:
Alone the word is こめ, but in compounds 米 is the usual reading: 米価 (rice prices), 新米 above. The same character also stands for America, as in 米国.
MEASURING:
Sold by the キロ, but cooked by the 合 — a traditional unit of about 180 ml that rice cookers and recipes still use.
CULTURAL NOTE:
Rice is Japan's staple crop, and the language keeps the trace: ご飯 means both 'cooked rice' and 'meal', so in everyday speech eating and eating rice are the same word.