This is the 13337th most frequent Russian word.
мысль
"Мысль" means "thought" in English.
Here, 'мысль' refers to a specific idea or concept that has come to someone's mind.
У меня возникла хорошая мысль.
I had a good thought.
In this case, 'мысли' (plural) denotes the general intellectual activity or ideas of a person.
Её мысли всегда глубокие и философские.
Her thoughts are always deep and philosophical.
Here, 'мысли' refers to contemplations or reflections, particularly of a discouraging nature.