The difference between "he will be happy" and "he would be happy" lies in their tenses and the level of certainty or conditionality they express.
- "He will be happy":
- This sentence is in the simple future tense.
- It expresses a definite and straightforward statement about the future.
- It indicates that the person (he) is expected to experience happiness at some point in the future, and there is a high degree of certainty about this event occurring.
Example: After his exams are over, he will be happy.
- "He would be happy":
- This sentence is in the conditional mood, specifically the simple conditional tense.
- It implies that the person's happiness is contingent on a certain condition being met.
- It is often used to discuss hypothetical situations or possibilities.
- It can also be used to express a polite request or suggestion.
Example 1 (hypothetical): If he won the lottery, he would be happy. In this example, the person winning the lottery is a hypothetical situation, and the sentence suggests what his emotional state would be under that circumstance.
Example 2 (polite request): If you could help him, he would be happy. Here, the sentence implies a polite request, indicating that the person's happiness depends on the help being offered.
In summary, "he will be happy" states a straightforward fact about the future with a high level of certainty, while "he would be happy" introduces a conditional aspect, suggesting a possibility or a dependency on a particular condition being fulfilled.