"In essential" is a phrase commonly used to describe something that is necessary or crucial. However, there are other phrases and words that can be used as synonyms to express the same idea. "Indispensable," "vital," and "key" are examples of synonyms that have similar meanings to "in essential." Additionally, words like "fundamental," "necessary," "critical," and "imperative" can also be used to convey the idea of something being essential. Choosing the appropriate synonym depends on the context in which it is being used, as well as the writer's intended tone and style. All of these synonyms can be used to emphasize the importance of certain elements in different contexts.