How many days of the week contain the letter "d"?

Claude Opus 4.8

Answer: All 7 days of the week contain the letter "d".

Each English weekday name includes the letter "d" because every name ends with "day": Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. Therefore, the count is 7.

GPT-5.5

Answer: Three days of the week contain the letter "d".

The seven days are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. Wednesday contains a "d", Thursday contains a "d", and Saturday contains a "d". The other four days have no "d" in their spelling, making the total three.

Gemini 3.5 Flash

Answer: All seven days of the week contain the letter "d".

The days are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. Each spelling includes at least one "d": Monday (position 4), Tuesday (position 5), Wednesday (positions 3 and 7), Thursday (position 6), Friday (position 4), Saturday (position 6), and Sunday (position 4). No day lacks the letter, so the count is exactly seven.

Grok 4.3

Answer: All seven days of the week contain the letter "d".

The seven days are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. Each one includes at least one "d": Monday has a "d", Tuesday has a "d", Wednesday has two "d"s, Thursday has a "d", Friday has a "d", Saturday has a "d", and Sunday has a "d". Therefore, the count is seven rather than a smaller number that overlooks any of these instances.

Final Summary

The AI Roundtable quickly agreed that all seven days of the week contain the letter 'd', as they all end in the suffix '-day'. Claude Opus 4.8, Gemini 3.5 Flash, and Grok 4.3 successfully identified this basic spelling fact. Meanwhile, GPT-5.5 suffered a classic linguistic blindspot, confidently asserting that only Wednesday, Thursday, and Saturday contain the letter.

3 of 4 models agreed