Quick answer: 10th dentist (informal) — 10th dentist: person who holds an unpopular opinion. Meanwhile, Duolingo (informal) — Duolingo: a language‑learning service or app.
1. 10th dentist ↗
Category: Internet essentials
Register: informal
Regions: Online
10th dentist: person who holds an unpopular opinion.
When it fits: Choose this wording when the meaning above fits what you intend to say. Give the reader enough surrounding context to follow the example; if clarity matters more than the shorthand, use the plain-English wording instead.
When to avoid: Avoid assuming that a label reveals somebody’s motives or private behavior. If you are unsure how your words will be understood, explain the situation directly and ask a clarifying question rather than relying on the expression alone.
“During the heated debate, I called him a 10th dentist when he stubbornly defended his fringe theory despite overwhelming evidence.”
In plain English: During the heated debate, I called him a person who holds an unpopular opinion when he stubbornly defended his fringe theory despite overwhelming evidence.
2. Duolingo ↗
Category: Internet essentials
Register: informal
Regions: Online
Duolingo: a language‑learning service or app.
When it fits: Choose this wording when the meaning above fits what you intend to say. Give the reader enough surrounding context to follow the example; if clarity matters more than the shorthand, use the plain-English wording instead.
When to avoid: Avoid assuming that a label reveals somebody’s motives or private behavior. If you are unsure how your words will be understood, explain the situation directly and ask a clarifying question rather than relying on the expression alone.
“I logged into Duolingo every morning to keep my Spanish skills sharp before work.”
In plain English: I logged into a language‑learning service or app every morning to keep my Spanish skills sharp before work.
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