Highlighter is a variant of felt-tip pen with water-based ink that is used for marking of text. It uses vivid, translucent color that makes text stand out more without obscuring it. It is very popular with students who use them to mark important parts of text for easier learning.
Many come in bright, often fluorescent and vibrant colors. Being fluorescent, highlighter ink glows under black light. The most common color for is yellow, but they are also found in orange, red, pink, purple, blue, and green varieties.
Highlighters are available in multiple forms, including some that have a retractable felt tip or an eraser on the end opposite the felt. Other types of highlighters include the trilighter, a triangularly-shaped pen with a different-coloured tip at each corner, and ones that are stackable.