A word used to describe an important action or suggestion is a subjunctive verb. It is not a specific grammatical form or tense, but is instead called a type of mood. This means that it is used only in specific situations, and may not always be necessary to express an idea in a certain way. The subjunctive mood exists in English, but it isn't very common, and isn't always distinguishable from other moods or tenses at first glance. Usually, in English, a subjunctive verb is used more in writing than in speech, although some other languages use it more commonly.
The subjunctive form of a verb is a shortened version of its infinitive. For example, the subjunctive of the verb "to make" would be simply "make." A subjunctive verb is usually used with a relatively small list of specific expressions, and this is how the mood can be reliably detected in context. The phrase "it is essential that we be on time" contains the subjunctive because it describes urgency with the proper verb form. By contrast, the phrase "being on time is important" doesn't use the proper verb form, so it doesn't use the subjunctive.
Although subjunctive doesn't occur often in ordinary speech, a few common expressions still use it. The phrase "if I were you" is a good example of this, where something is being suggested. Formal language, particularly that with a religious overtone, is also peppered with the occasional subjunctive verb, for example "be that as it may." There are actually three different types of subjunctive speech, which all serve the same general function of expressing wishes, demands, or suggestions.
Subjunctive verb use has been uncommon since at least the beginning of the twentieth century, but it was more common in earlier forms of English, such as Old English. Old English existed hundreds of years before the time of Shakespeare, whose works are actually classified as Modern English. The reason that subjunctive has almost died out as the English language evolved, but still remains a fixture of some foreign languages, isn't clear. Despite its decline, it has existed in the English language for more than a thousand years.
If the subjunctive mood disappears in the future, that doesn't necessarily mean that English will lose its richness as a language. Moods, tenses, and words have appeared and disappeared in the language for centuries, and that is a natural part of language evolution. When and if the subjunctive disappears, the meanings it conveys will probably not disappear with it, so it will just need to be expressed another way.