1. She goes to a yoga class three times a week.
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What does 'class' mean here? Is it classroom or lesson?
It's held in a workout room and it's considered a session -- could be called a lesson, I guess.
https://www.google.com/search?q=yoga+class&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjitOj77ZPfAhWl7YMKHZcvBNcQ_AUIDygC&biw=1440&bih=703
In the sentence "She goes to a yoga class three times a week," the word "class" refers to a specific session or gathering where people come together to participate in yoga exercises and instruction. In this context, "class" does not mean a physical room like a classroom, but rather the organized activity of practicing yoga.
To understand the meaning of a word in a sentence, it can be helpful to look at the surrounding words and the overall context of the sentence. In this case, the mention of "yoga" indicates that "class" refers to a group or gathering focused on yoga exercises.