How many words do you know? As Bill Clinton might say, it depends on how you define the word “word.” A new study suggests that—if you’re excluding proper nouns, multiword phrases (like “kick the bucket”), and derived words (like “helplessly,” from “help”)—the typical English-speaking American knows about 42,000 of these so-called “lemmas” by the age of 20, UPI reports. The study, published this week in Frontiers in Psychology, asked more than 220,000 people to review a list of 100 words—some real and some made up—to decide which were actual entries in the dictionary. High scorers—those in the top 5%—knew an average of 52,000 lemmas, whereas low scorers—those in the bottom 5%—knew an average of 27,000. If you want to see where you fall on that scale, you can take the online test here.