Mass lexical comparison is when you take a lot of words and compare them to each other. Imagine you have a toy box with many different toys, you want to see which toys are the same and which ones are different. This is what researchers do with words.
They take two or more piles of words, for example, one pile with all animal names and another with all food names. They then put them side by side and start looking for words that belong with each other. For example, a cow belongs in the animal pile, and grass belongs in the food pile.
This method is used to find similarities and differences between words. By doing this, researchers can learn more about how people communicate using language. It's like playing a game of "match the pairs" but instead of pictures on the cards, it's words.