The term WORD AFTER 'LITMUS' OR 'LAB' is TEST, which is a four-letter word. A TEST is an assessment used to measure a person's knowledge, skills, aptitude, physical fitness, or classification in many other topics. Tests are often used in education, professional certification, psychology, and other fields. Litmus tests and lab tests are two types of tests that are used to measure different things. Litmus tests are used to measure the acidity or alkalinity of a solution, while lab tests are used to measure the presence of certain substances in a sample.