How write English numbers?

To write English numbers, you typically use Words for numbers one through nine (e.g., one, two, three) and numerals for 10 and above (e.g., 10, 25, 100). In formal writing, it's common to spell out numbers at the beginning of sentences. When writing large numbers, you can separate them into groups using commas for clarity (e.g., 1,000; 10,000). Always consider the context and style guide requirements when deciding whether to use Words or numerals.