HSK 2
X 也就是说 / 也就是 Y
Apposition / 'that is to say.' Used to restate or clarify in a more formal, expository register than 就是.
Hear It in Real Episodes
This pattern appears in 4 Fluentide episodes:
The Pentagon Released 162 UFO Files: Inside Are 'Orbs Spawning Orbs' and Strange Lights from the Moonmedium
也就是说：一个橘色的大球，忽然变成大球加几个红色的小球。
The US Government Finally Opened the UFO Files: What's Inside?easy
也就是说：一个大的橘色球，忽然变成了一个大的，加几个小的。
A Ship at Sea: Over a Hundred People Who Can't Go Homeeasy
也就是说，你得了这种病，不会传给身边的人。
The White-House-Burning Joke: How Charles III Reset US-UK Relations With One Banquetnormal
也就是说，二百五十年前，美国人是英国国王的子民。
Related Grammar Patterns
又...又...Both... and... Connects two qualities or states that exist s...关于……Reach for 关于 when you need to announce the topic of somethin...如果... (就)...Reach for this whenever you want to set up a condition and a...这就叫'...'Reach for this when you want to label what just happened wit...正好是...'It just happens to be...' Highlights striking timing.不能...'Cannot...' / 'Must not...' Used for prohibitions and rules.