1. When "however" introduces a contrasting idea:
* Comma: If "however" introduces a contrasting idea within the same sentence, it is usually followed by a comma.
* Example: "The weather was terrible, however, the concert was amazing."
2. When "however" begins a new sentence:
* Period: If "however" begins a new sentence, it is followed by a period.
* Example: "The weather was terrible. However, the concert was amazing."
3. When "however" introduces a parenthetical phrase:
* Commas: If "however" introduces a parenthetical phrase (a phrase that could be removed without changing the meaning of the sentence), it is usually followed by commas.
* Example: "The weather, however, was terrible."
In summary:
* Comma: If "however" is within the same sentence.
* Period: If "however" starts a new sentence.
* Commas: If "however" introduces a parenthetical phrase.