| 自 |
zì rè | to heat up by itself; (attributive) self-heating (esp. of meal kits heated with a water-activated pack) |
| 自 |
zì | (bound form) self; oneself / from; since / naturally; as a matter of course |
| 热 |
rè | to warm up / to heat up / hot (of weather) / heat / fervent |