/**
 * Return a boolean value number of the letters in a string.
 *
 * @param text String input to get letters count from.
 * @param countNumbers boolean value to determine if numbers should be counted as letters.
 *
 * @returns Number of letters and numbers (if requested) in a string.
 * @example
 * count('Hello, world!'); // 10
 * count('Hello0 world', true); // 11
 */
export declare function count(text: string, countNumbers?: boolean): number;
/**
 * Counts the number of words in a string.
 * Words are defined as sequences of letters, numbers, and apostrophes separated by whitespace.
 *
 * @param text String input to count words from
 * @returns Number of words in the string
 * @example
 * countWords('Hello, world!'); // 2
 */
export declare function countWords(text: string): number;
/**
 * Counts the number of sentences in a string.
 * Sentences are defined as sequences of text ending with ., !, or ? followed by whitespace or end of string.
 * Text without any sentence-ending punctuation is considered to be a single sentence.
 *
 * @param text String input to count sentences from
 * @returns Number of sentences in the string
 * @example
 * countSentences('Hello world! How are you?'); // 2
 */
export declare function countSentences(text: string): number;