"Once a year" is an adverb (like "sometimes" or "often") and therefore can't be made plural.
It stay the same even when describing multiple actions, people, or events. (for example, "Christmas and Easter both happen once a year," or "John and I go to the mountains once a year."
If you would like to describe something that happens more often, try "twice a year", "three times a year", "ten times a year", "many times a year", or "once a month".
For something less often try "once every two years" or "once every three years".
The plural form of two-year-old is two-year-olds.
The plural noun is years. To spell out year names, use the hundreds of years, followed by the last two digits as a number. (Use "oh" for a leading zero) 1840 = eighteen forty 1700 = seventeen hundred 1901 = nineteen oh one 2012 = twenty twelve Even thousands are spoken as thousands: 2000 is "two thousand."
Once a year is correct.
The plural of the word blossom is blossoms. As in "the blossoms look nice this year".
You seem to be having trouble figuring out which word is the noun that needs to be the plural. Which thing do you have more of - twenty, year, or old? Twenty years is the modifier for old. You have two twenty year olds.
The plural form of two-year-old is two-year-olds.
The plural form of thirteen year-old is thirteen year-olds.
The possessive form of the plural noun facilities is facilities'.Example: All of our facilities' managers meet once a year.
The plural form of the noun year is years.The plural possessive form is years'.example: I have five years' experience as a chicken plucker.
The plural noun is years. To spell out year names, use the hundreds of years, followed by the last two digits as a number. (Use "oh" for a leading zero) 1840 = eighteen forty 1700 = seventeen hundred 1901 = nineteen oh one 2012 = twenty twelve Even thousands are spoken as thousands: 2000 is "two thousand."
The word 'years' is the plural form of the singular 'year'.
The noun year is the singular form.The plural form is years.example: This year has gone well, better than the last few years.
To make the word "year" plural, you simply add an "s" to the end, changing it to "years."
Yes, the plural form is marshes. Example:The shoreline of Chicago was once a series of marshes.
The word is "I" which becomes "is".
Once a year is correct.
Weeks. As in, "I will be going on holiday for two weeks" or "There are 52 weeks in a year" If something occurs once a week, it is described as "weekly" Hope that helps