For anyone who has been confused by Opus, Flash and GPT-5.5
No. 54How AI WorksPart 12 of 14Fact-checked Oct 3, 2026Updated Oct 4, 2026
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Claude Opus 5.5. GPT-4o mini. Looks like gibberish? It's really just three pieces: whose it is, how big, and which version. First, the brand. Every name has a story.
Gemini is Latin for twins. Two teams at Google merged into one. Grok comes from a sci-fi novel. It means to understand completely. Llama is an acronym that happens to spell an animal.
And Claude? Reportedly a nod to Claude Shannon, the father of information theory. The company has never confirmed it. Next, size. Claude uses poems: a haiku is small, a sonnet is medium, and an opus is the big one. The newest tier: Mythos and Fable. Same ability, but Fable has safety rails, so everyone can use it.
Finally, the version. Bigger means newer. But after o1, OpenAI jumped straight to o3. Because a British phone company is already called O2. Even OpenAI's boss joked: our naming deserves the mockery. So next time you see one, break it into three: whose, how big, which version.
Only compare numbers within one company. Across companies, ignore the name. What counts is how well it works for you.
1
In one sentence
A model name is usually three pieces stuck together: whose it is, how big, which version.
2
You already know how to read these
PHONE
iPhone 17 Pro
Brand iPhoneVersion 17Tier Pro
A I
GPT-4o mini
Brand GPTVersion 4oSize mini
Same parts — each company just puts them in a different order.
3
The brand: every name has a story
ClaudeAnthropicReportedly a nod to Claude Shannon, father of information theory. The company has never officially confirmed it.
GeminiGoogleLatin for "twins": two teams merged into one. Also NASA's Gemini program, the step before the Moon landings.
GPTOpenAIFirst letters of three words: it writes new things, it read huge amounts of text first, and it uses a design called a "Transformer".
GrokxAIFrom the 1961 sci-fi novel Stranger in a Strange Land. It means "to understand something completely".
LlamaMetaShort for "Large Language Model Meta AI" — which happens to spell an animal.
MistralFrench companyA cold, strong wind in southern France. The company is French.
QwenAlibabaChinese name Tongyi Qianwen, "a thousand questions". The "wen" means "ask".
DeepSeekChinaMeans exactly what it says: seek deep. Its V models chat; R1 is the one that thinks before it answers.
4
The size: Claude uses poem lengths
Anthropic's CEO has said they settled on a poetry theme — the longer the poem, the bigger the model.
HaikuA three-line Japanese poem. Small: fastest and cheapest.
SonnetA 14-line poem. Medium: the everyday workhorse.
OpusLatin for "work" — think of a big, thick book. Large: smartest, and most expensive.
OTHER COMPANIES
Google: Flash (fast), Pro (main) OpenAI: add mini or nano for small
5
The newest tier: myth and fable
In 2026, Claude added a tier above Opus.
MYTHOS
Greek for "story, myth". The strongest one, for a few organizations only.
FABLE
Latin for "that which is told". The same ability, with safety rails, open to everyone.
Anthropic itself says the two words are close cousins.
6
The version: simple, until it isn't
Bigger number means newer; a ".5" is a smaller update. But sometimes it goes sideways:
SKIPPING
OpenAI made o1, then jumped straight to o3.
A British phone company is called O2, and they wanted to avoid a trademark clash.
GOING BACKWARDS
First GPT-4o, then 4.5, and then 4.1.
The "o" in 4o means "omni": it can see, hear and speak.
"How about we fix our model naming by this summer and everyone gets a few more months to make fun of us (which we very much deserve) until then?"
— Sam Altman, OpenAI CEO, on X, April 14, 2025
7
A common mistake
Only compare numbers within one companyClaude Opus 5.5 and GPT-5.5 share a number by coincidence. It doesn't mean same generation or same strength. Across companies, names tell you nothing.
Next time, break it into three
Whose, how big, which version. Small for speed, large for hard problems. Across companies, ignore the name — try them yourself.
