| Globally extinct | The species is extinct in the whole world, both in the wild and in cultivation. |
| Presumed nationally extinct | the species is extinct in Singapore but still survives in another country. It is not recorded within the last 30 years for plants, or 50 years for animals. |
| Critically endangered | There are fewer than 50 mature individuals, or if more than 50 mature individuals but less than 250, with some evidence of decline or fragmentation. |
| Endangered | There are fewer than 250 mature individuals, and no other evidence of decline or fragmentation. |
| Near threatened | Approaching but not yet reaching the threshold for the above criteria. |
| Least concern | Not approaching the threshold of 250 mature individuals. |
| Data deficient | The information is not adequate to make an informed assessment. |
| Common | There are more than 1000 mature individuals. |
| Exotic and not endangered elsewhere | The species was introduced into Singapore from elsewhere. |
The Singapore Red Data Book 2008
This categorization with specific thresholds applies only to Singapore.