几 / 机: how to tell them apart
机 has 木 on the left (飞机, 手机).
几 jǐ — how many; a few
几
| 几岁 | jǐ suì | how old | 1A lesson 3 |
机 jī — machine
机
| 飞机 | fēi jī | aeroplane | 1B lesson 16 | |
| 折纸飞机 | zhé zhǐ fēi jī | to fold paper planes | 2B lesson 11 | |
| 司机 | sī jī | driver | 3A lesson 1 | |
| 灵机一动 | líng jī yī dòng | to have a sudden idea | 4A lesson 2 |