• (a piece of) playground equipment, a slide
• a picnic table, picnic tables, a park, parks, a pond, ponds
• a giraffe, giraffes, a tiger, tigers
• the London Zoo, the Bronx Zoo, the Taipei Zoo

• Alice, a software engineer, to design software
• Ms. Rigas, an engineering professor, to teach engineering
• Terry, a barista, a coffee shop, to make a latte = to make a caffe latte
• Terry, a bartender, a bar, to make a cocktail
• Dr. Chavez, an ENT doctor, an ear-nose-and-throat doctor, at work, at a park, on a break
• on break = on a break
• Greta, a fild producer
• Fatima, in class, a middle school
• Mr. Gomez, a high school teacher, in class
• Rachel, Olivia, Emma, Sophia
• Oscar, an elementary school
• Erik, Noah, at recess

• Polly, Carol, Kelly, in kindergarten, to play in a sandbox
• Mrs. Donovan, an elementary school teacher
• Jared, to swing on a swing
• Lucy, at the park, to play with bubbles
• Phoebe, at the zoo, pointing to (at) an exhibit
• Thelma, at the llama exhibit
• Ethan, at the camel exhibit
• Becky, at the aquarium, to look at some fish
• Liz, a ray
• Tina, an unusual fish

• This is Alice. Alice is a software designer. She’s at work. She’s working. Alice is designing software.
• This is Ms. Rigas. Ms. Rigas is an engineering professor. She’s at work. She’s working. Ms. Rigas is teaching an engineering class.
• This is Dr. Chavez. Dr. Chavez is an ENT doctor. She’s an ear-nose-and-throat doctor. Ear-nose-throat: ENT. She’s an ENT doctor. She works at a clinic. Dr. Chavez is at work, but she’s not working right now. She’s at a park on a break. She’s on a break at work.
• This is Erik and Noah. They’re in elementary school. They’re at school but they’re not in class. They’re at recess.
• This is Polly, Carol, and Kelly. They’re in kindergarten but they’re not in class. They’re at recess. They’re playing in a sandbox.

No article is used when a train station is named (see Video 008):

• The train is at the station.
• The train is at Grand Central Station.
• The train is at Shinjuku Station.

The article is optional when a bus stop is named:

• The train is at the bus stop.
• The train is at (the) Jackson Street bus stop.

Articles are used for zoos and aquariums regardless of whether they are named.

• Phoebe's at the zoo. Phoebe's at the San Diego Zoo.
• Thelma's at the zoo. Thelma's at the Bronx Zoo.
• Becky's at the aquarium. Becky's at the Florida Aquarium.
• Liz is at the aquarium. Liz is at the Lisbon Oceanarium.

Note: There are exceptions to this rule and English speakers are not always consistent.

• The first woman to be a curator at the London Zoo was Evelyn Cheesman, in 1920.
• Many of the species in London Zoo could not be seen anywhere else in the country...
• (Examples from Wikipedia)

Recess is a school break during which children play, usually outside.

Typically, kindergartners and other elementary school children have a morning recess, a lunch recess, and maybe an afternoon recess.

In junior high and high school, students typically do not have recess. Instead, they have short breaks between classes and a lunch break.

When taking a lunch break, the preposition "at" is used: to be at lunch. This is true for workers and students.