A tree who can say three words in one order, and who is understood perfectly by exactly one person.
Groot has three words and the films get an extraordinary amount out of them. The joke is that only Rocket understands him. The better joke is that the audience starts to as well, somewhere in the first film, without anything having been explained.
He is also the run’s clearest piece of structural design. Each film gives him a different age, so the same character is a bodyguard, then a toddler, then a teenager, then an adult, across nine years of releases. Nobody else in this catalogue is allowed to grow up.
Show detailsWhether it is the same Groot
The original Groot dies at the end of the first film. What is left is a sapling, and the reference article is direct about what that means: James Gunn has described the new Groot as the original’s son, and Rocket’s own entry lists Groot as his adopted son.
So by the article’s own framing, films two through six are a different individual from film one. Its summary nonetheless counts six films for one character, and this catalogue follows the summary. It is exactly the same question the entry for Gamora has to answer, and it is answered here the same way, which is: record what the source counts and say plainly where the source is in two minds.