When dividing most common English phrases into topics, it is wise to know how important it is to learn what a language function is. Namely, functions in English are phrases used to express a specific purpose. They are different from phrases based on a topic, because they are much more general, and can be used in any situation, as explained in this video about functions in English:

Phrases and Language Functions in English

Throughout the years, scholars and linguists have been intrigued by the intricate nature of English language functions and phrases. Across different discourse types, it is evident that such phenomena are far from uniform but rather vary depending on language usage, context, and intention. This paper aims to delve deeper into the nuances of English phrases and language functions while highlighting their differences.

Language functions in English refer to how expressions are used to achieve different communicative purposes. These can range from making requests or giving directions to expressing emotions or opinions. On the other hand, phrases in English denote a group of words functioning as a single unit within a sentence. Phrases can be nominal, verbal, adjectival or adverbial, among others, each with its unique meaning and position in a sentence structure.

The difference between these two concepts can be attributed to their distinct nature. Whereas language functions relate to pragmatics, syntax governs phrases' rules and structures. The identification of various types of phrases helps clarify their relationship with other parts of speech in sentences. In contrast, understanding the function of language enhances communication effectiveness by aligning our expressions with our intentions accurately. Thus, comprehending variations in phrases and language functions is crucial for effective communication in diverse settings.

A list of most commonly used English functions :

1. Asking for and giving opinions
2. Explaining and justifying
3. Asking for clarifications
4. Giving clarifications
5. Expressing agreement
6. Expressing disagreement
7. Interrupting
8. Describing people
9. Introducing oneself and giving personal info
10. Talking about likes and dislikes
11. Talking about interests
12. Expressing preferences
13. Making complaints
14. Giving warnings
15. Asking for advice
16. Giving advice
17. Asking for more detailed information
18. Making suggestions and responding to suggestions - accepting & declining
19. Making plans and
20. Making proposals, talking in favour or against a proposal
21. Making predictions
22. Expressing degrees of certainty and uncertainty
23. Asking for descriptions
24. Giving descriptions
25. Making comparisons
26. Making generalizations
27. Expressing disappointment
28. EFL ESL Invitation phrases
29. Small talk phrases

Now, can you see that for each set of phrases based on a topic, one can use a number of appropriate functions in English?
For example, if you learn functions for interruption, and you can successfully use them in any situation.

It is also important to emphasize that when listing functions, it is always wise to list them in an order, according to the level of formality, so that a student can tell which functions are most appropriate in a specific context.

Now, how essential is it for a student to be able to tell the difference between functions and phrases ?

It's not important at all: if a teacher subtly introduces all these useful phrases and functions in English, students needn't know what they are called, but they should be taught to use them appropriately. If they do so, they'll feel much more confident when speaking English and such knowledge can only add up to their fluency.