| Share | Phrase |
|---|
| 11.06% | optional [importance] feature |
| 8.47% | optional [importance] object |
| 6.25% | optional [importance] use |
| 6.14% | optional [importance] step |
| 6.07% | optional [importance] valve |
| 5.50% | optional [importance] section |
| 4.34% | optional [importance] it |
| 3.69% | optional [importance] additive |
| 3.10% | optional [importance] assembly |
| 2.77% | optional [importance] addition |
| 2.50% | optional [importance] component |
| 2.42% | optional [importance] spring |
| 2.40% | optional [importance] equipment |
| 2.39% | optional [importance] condition |
| 2.27% | optional [importance] sensor |
| 2.25% | optional [importance] seal |
| 2.21% | optional [importance] position |
| 2.15% | optional [importance] purification |
| 2.00% | optional [importance] design |
| 2.00% | optional [importance] means |
| 1.90% | optional [importance] switch |
| 1.76% | optional [importance] system |
| 1.71% | optional [importance] line |
| 1.62% | optional [importance] reservoir |
| 1.52% | optional [importance] number |
| 1.48% | optional [importance] cycle |
| 1.45% | optional [importance] device |
| 1.38% | optional [importance] adjustment |
| 1.30% | optional [importance] point |
| 1.28% | optional [importance] circuit |
| 1.16% | optional [importance] unit |
| 1.13% | optional [importance] portion |
| 1.12% | optional [importance] member |
| 1.05% | optional [importance] element |