This is the 720th most frequent Danish word.
lagde
"Lagde" means "put" or "laid" in English, as the past tense of "lægge" (to lay/place).
Here, 'lagde' is the past tense of 'lægge', showing an action of placing.
Jeg lagde bogen på bordet.
I put the book on the table.
In this case, 'lagde' is used in the expression 'lagde mærke', meaning 'noticed'.
Han lagde mærke til detaljerne i maleriet.
He noticed the details in the painting.
Here, 'lagde' describes the action of lying down in the past.