Full stops and commas are punctuation marks. A full stop ends a sentence. A comma shows a pause, breaks up a list or separates parts of a sentence. Full stops are easy. They always go at the end of a ...

The Price to Earnings (P/E) ratio, a key valuation measure, is calculated by dividing the stock's most recent closing price by the sum of the diluted earnings per share from continuing operations for ...

Adding extra information to a sentence (or paragraph) using brackets, dashes or commas. If you take it out again, the passage should still make grammatical sense. "The case was worn - and very full - ...