This is the 211th most frequent Spanish word.
poner
To put, place, or set.
Here, 'pone' (in the reflexive form 'se pone') indicates a change of state or becoming something, in this case, becoming sad.
Ella siempre se pone triste cuando escucha esa canción.
She always becomes sad when she hears that song.
In this example, 'poner' is used to mean placing or positioning an object in a location.
¿Puedes poner el libro en la mesa, por favor?
Can you put the book on the table, please?
In this sentence, 'poner' is used in the sense of arranging or placing items in an organized manner for a specific purpose.