Pronunciation: [jˈi͡əɹ ˈə͡ʊld] (IPA) 
The spelling of the phrase "year old" can be tricky for non-native English speakers due to the pronunciation of the word "year". In IPA phonetic transcription, "year" is pronounced as /jɪər/ with a silent "e". Therefore, when writing "year old," it is important to omit the "e" and use "year" as /jɪər/. For example, "He is 5 years old" would be written as "He is 5 years old" with the correct pronunciation being /jɪərz əʊld/.
"Year old" is a phrase used to indicate the age of a person, object, or concept that has completed one year since its birth, creation, or inception. It constitutes an adjective phrase that specifically describes the duration of existence, development, or lifespan of something within the span of one year.
When applied to a living being, such as a human or animal, "year old" refers to the period that has transpired since the day of birth, marking the completion of one full year of life. For instance, a "ten-year-old" individual has lived for a decade, having experienced the events, growth, and learning opportunities that come with that duration of time.
When referring to non-living things, the term "year old" signifies the time that an object or concept has been in existence or use. It aids in contextualizing the age or duration of a specific item, entity, or idea. For example, a "one-year-old car" indicates that the car is one year since its manufacture or purchase.
In summary, "year old" serves as a descriptor to specify the age or duration of something within the scope of a year, offering a concise way to convey the length of time since an event, birth, creation, or start.
"Year" is derived from the Old English word "gear", which itself can be traced back to the Proto-Germanic word "jǣram". This word is ultimately derived from the Proto-Indo-European root "yeH₁r", meaning "to go, travel". The addition of the word "old" to "year" simply indicates the age of an individual or object, forming the phrase "year old".
