Here is a summary of the details provided in the video:

• Definition and Function: The subjunctive mood is a way of expressing things that are not currently happening, such as wishes, demands, or imaginary situations. It represents a mood rather than a tense to show an attitude of urgency, unreality, importance, or desire rather than cold, hard facts.
• Demands and Suggestions: When following verbs like insist, recommend, demand, or suggest with "that," the subsequent verb takes its base form. Any "-s" or "-es" ending is dropped regardless of subject pronouns (e.g., using "I suggest that she wait here" instead of "she waits") to add authority and formal structure to a request.
• Hypothetical and Imaginary Situations: To show that a statement is impossible or contrary to reality, standard factual terms like "I was" or "he was" shift to "were" (e.g., "if I were you" or "I wish I were taller").
• Fixed Idiomatic Expressions: Certain older, "frozen" expressions remain in the language as subjunctive fossils, such as "God save the Queen," "if need be," or "suffice it to say". These are treated as fixed chunks to memorize rather than analyze.

Related notes

• Grammar C1 - Advanced Discourse Markers
• Grammar C1 - Hedging and Vague Language
• Grammar C1 - Ellipsis and Substitution
• Grammar C1 - Nominalization
• Grammar C1 - Mixed Conditionals
• Grammar C1 - Inversion with Negative Adverbials
• Grammar C1 - Advanced Participle Clauses
• Grammar C1 - Causative and Impersonal Reporting
• Grammar C1 - Cleft Sentences