Answer: To write 1000 in Roman numerals, we can use “M.” “M” represents the number 1000 in Roman numerals.

Basic Rules to Interpret Roman Numerals

• Basic Symbols: Roman numerals are composed of basic symbols to represent the: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000).

• Repeated Symbols: If a Roman numeral has a symbol repeated, the values are added together. For example, II is 1 + 1 = 2, and XXX is 10 + 10 + 10 = 30.

• Subtractive Notation: When a smaller Roman numeral appears before a larger one, it is subtracted from the larger one.
  For example, IV represents 5 – 1 = 4, and IX represents 10 – 1 = 9.

• No More Than Three Repeats: A Roman numeral cannot have more than three consecutive identical symbols. To represent larger numbers, subtractive notation is used. For example, 4 is IV (one less than 5), not IIII.

• Order of Symbols: Roman numerals are read from left to right, and symbols are combined according to the rules above.

• Larger values should always come before smaller ones. For example, 98 is written as XC (10 before 100, with a subtraction).

• Successive symbols cannot increase in value by more than tenfold. For example, 99 is not IC (100 – 1) but XCIX (10 before 100, 1 before 10, and 10 before 1).