What rule applies to the word "desire"?

 In the English language, the word "desire" can be subject to several grammatical rules depending on how you are using it. If you are asking about how to adjust the form of the word according to different contexts, here are some key rules to consider:

1. **As a Noun**: When "desire" is used as a noun, it doesn't require any modification to show plural forms because "desire" is an uncountable noun. For example: "Her desire for knowledge is evident."

2. **As a Verb**: When "desire" is used as a verb, it can change form to fit different tenses. For instance: - Present simple tense for he/she/it adds an "s": "She desires a successful career." - In the past simple tense, it becomes "desired": "They desired a quiet evening at home."

3. **Adding Suffixes**: When forming adjectives or other noun forms, you often add suffixes like "-able" or "-ous" (desirable, desirous).

4. **Verb Agreement**: As a verb, "desire" must agree with the subject in number and person. For example, "I desire," "he desires," "they desire," and so on.

These are some of the rules that apply when using the word "desire" in English. Depending on what specifically you are asking about, there could be many other relevant rules as well, such as those regarding compound tenses or modal verbs.