classes ([a-z])

 classes ([a-z])

The regular expression [a-z] is a character class that matches any single lowercase letter from 'a' to 'z', inclusive. 

Explanation of [a-z]

• [] (Square Brackets): These define a character class (or set). Any single character within the input string that matches any character in the set will satisfy this part of the expression.
• a-z (Hyphenated Range): The hyphen inside the square brackets specifies a range of characters. It includes every character in the range between the start character ('a') and the end character ('z'), based on the character encoding (typically ASCII or Unicode). 

Key Points

• Single Character Match: [a-z] matches one single character, which can be 'a', 'b', 'c', ..., all the way to 'z'.
• Case Sensitivity: By default, this expression is case-sensitive and will not match uppercase letters like 'A', 'B', etc. To match both cases, you would use [a-zA-Z].
• Multiple Occurrences: To match a sequence of one or more lowercase letters, you would append a quantifier, such as the plus sign (+) for one or more ([a-z]+) or the asterisk (*) for zero or more ([a-z]*).
• Context: The behavior can be slightly different depending on the specific regular expression engine or programming language (e.g., Python, JavaScript, Java), but the core concept of a lowercase character class remains consistent.