| O | A B C D E F G H I K L M N O P R S T U V W Z |
| Word | Description |
| Open planting site | A site within a garden where sunlight is available for most of the day. |
| Order | A category of taxonomic classification ranking above the family and below the class. Group of families. |
| Ovary | The female part of the flower containing the ovules which after pollination and fertilization become the seeds. |