A compound word is formed by joining two complete, unchanged words into one — unlike a portmanteau, which blends pieces of two words together. "Sunflower" is a compound word: sun and flower, both fully intact, just pushed together. "Brunch" is a portmanteau: breakfast and lunch, neither one intact, both trimmed down and fused at the sound where they overlap. The two techniques sit right next to each other in how English builds new words, and mixing them up is one of the most common mistakes people make when they hear the word "portmanteau" for the first time.
The Three Types of Compound Words
Compound words show up in English in three different spellings, and which one a word ends up as is mostly a matter of how long it's been in common use rather than any fixed rule:
- Closed compounds are written as one word with no space or hyphen — "notebook," "rainbow," "haircut." These are usually the oldest or most frequently used compounds, since spacing tends to disappear the more a word gets used.
- Open compounds keep a space between the two words but function as a single unit of meaning — "swimming pool," "coffee table," "traffic light." You can't swap either half out without changing the meaning entirely, even though they're written separately.
- Hyphenated compounds sit in between, joined with a hyphen — "runner-up," "father-in-law," "six-year-old." English is inconsistent about when a compound moves from hyphenated to closed; "e-mail" became "email" for most style guides over time, following exactly this pattern.
Compound Words vs. Portmanteau — the Real Difference
This is the distinction worth getting right. A compound word keeps both original words whole — you can still see "sun" and "flower" completely intact inside "sunflower." A portmanteau cuts both words down and fuses them at a shared sound, so at least part of each original word is gone. "Motor" + "hotel" becoming "motel" is a portmanteau, because neither original word survives in full. If it had become "motorhotel," that would be a compound instead. The test is simple: if both full words are still readable inside the result, it's a compound. If either one has been trimmed, it's a portmanteau.
| Original Words | Result | Type |
|---|---|---|
| sun + flower | sunflower | Compound (both words intact) |
| breakfast + lunch | brunch | Portmanteau (both trimmed) |
| smoke + fog | smog | Portmanteau (both trimmed) |
| note + book | notebook | Compound (both words intact) |
| web + log | blog | Portmanteau (web trimmed to "b") |
Why This Distinction Matters for Naming
When you're deciding how to combine two names, this is really a choice between two different techniques, not just one. Keeping both names fully intact and pushing them together — "Sarah" + "Jane" becoming "SarahJane" — is the compound approach. It's clear and easy to read, but it doesn't feel as much like one unified name. Trimming and blending — "Sarah" + "Jane" becoming "Sarane" — is the portmanteau approach, and it's what makes a combined name feel like a genuine new word rather than two names glued together. Our Mix Names tool defaults to the portmanteau approach for exactly this reason, since it's what produces names that read naturally rather than looking like two names with the space removed.
The Bottom Line
A compound word joins two whole words with nothing removed. A portmanteau trims and fuses two words at a shared sound. Both are legitimate ways English creates new words, and both sit under the broader umbrella of a neologism — any newly coined term, however it was formed. If you're combining two names and want the blended, portmanteau-style result rather than a simple compound, see our companion piece on what two names combined are called for the full technique.