## What are the differences between "three years old", "three-year-old" & "3-yr-old"?

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I'm not sure which of the following statements is most appropriate in case of a seedling:

Three year old seedling

Three-year-old seedling

3-yr-old seedling


The third one seems to be a nice abbreviation, but I'm not sure if it's a good fit for a plant's description which is going to be used within an article.

Could you please explain what are the differences between them? I'd like to use the third one, is it appropriate for an article about plants (which should sound official)?

1The child was three years old. A three-year-old child can talk. If somebody doesn't beat me to it I'll check for use with seedlings and the abbreviation during the weekend. – Lucky – 2015-05-01T23:00:11.313

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possible duplicate of a ten years old boy or a ten year old boy. The issues of 3 vs. three and using an abbreviation are different questions.

– user3169 – 2015-05-01T23:16:22.090

1I think if you explain what quality you are looking for, that might help people to answer you. Is it a very official article or something more relaxed? Maybe any of them works fine though after the obvious mistake has been fixed. – karlalou – 2015-05-02T00:48:18.063

After reading only title and tomorrow being the Kentucky Derby, I thought someone was posing a question about horse racing. So sorry, off topic, but I couldn't help it. – Ast Pace – 2015-05-02T01:15:06.777

In my experience, abbreviations don't usually have different meanings. Just different spellings. I've only seen the hyphenated form (3-year-old) when referring to a specific child, vs something that happens to be 3 years old. – ryanyuyu – 2015-05-02T04:16:32.047

2Three-year*s*-old is just incorrect. A child is three years old. There were a group of three-year-olds at the playground. We just transplanted a three-year-old seedling. Two years ago we had 3 year-old seedlings but 2 of them died. – Jim – 2015-05-02T04:50:42.603

1As @Jim points out, the hyphenation links the concept; otherwise there would be possible confusion between "three year old seedlings"… is that 3 seedlings, each one year old, or is it a collection of three-year-old seedlings? "three year-old seedlings" is 3 plants, aged 1 year; "three-year-old seedlings" is any plural number of plants, but they are definitely all three years old. – gone fishin' again. – 2015-05-02T10:25:31.847

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1) A three years old seedling.

2) Three-years-old seedling

3) 3 yr old seedling.

The phrase #1 is grammatically incorrrect because when you use the word "old" to refer to the age of a person or thing, it's a postpositive adjective. For example, you can say "This seedling is three years old, but you cannot say "This is three years old seedling.

The phrase #2 is also incorrect. When you combine the words in the phrase "three years old" by hyphenating them to make it an adjective or a noun, you must use the singular noun (year). So the correct phrase is:

Three-year-old seedling.

As for the phrase #3, it should also be framed in the same pattern as #2 mentioned above;

3-yr-old seedling.

@Catija, Thanks for your correction. I have edited my answer. – Khan – 2015-05-02T10:58:12.533