The abbreviations of the ordinal numbers 1-31 are as follows:

1-10: 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th,

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11-20: 11th, 12th, 13th, 14th, 15th, 16th, 17th, 18th, 19th, 20th,

21-31: 21st, 22nd, 23rd, 24th, 25th, 26th, 27th, 28th, 29th, 30th, 31st

The changing rules of 1-100 ordinal words can be summarized as follows:

1. The first category:

For example, first (1st) is the first, second (2nd) is the second, and third (3rd) is the third.

There are only three such ordinal words and require special memory. The abbreviations in parentheses are composed of Arabic numerals followed by the last two letters of the corresponding ordinal number.

2. The second category:?

There is fourth (4th), fifth (5th), sixth (6th), seventh (7th), eighth (8th) eighth, ninth (9th) ninth, tenth (10th) tenth, eleventh (11th) eleventh, twelfth (12th) twelfth, thirteenth (13th) thirteenth, fourteenth (14th) Fourteen, fifteenth (15th) Fifteenth, sixteenth (16th) Sixteenth, seventeenth (17th) Seventeenth, eighteenth (18th) Eighteenth, nineteenth (19th) Nineteenth, ordinal words of this type** *There are sixteen.

Their formation requires adding the suffix -th after the corresponding cardinal number. Pay attention to the spelling of the four words fifth, eighth, ninth, and twelfth.

3. The third category:

For example, twentytieth (20th) twentieth, thirtyth (30th) thirtyth, fortieth (40th) fortieth, fiftieth (50th) Fifty, sixtieth (60th) sixtieth, seventieth (70th) seventieth, eightieth (80th) eightieth, ninetieth (90th) ninetieth.

This category is all ordinal words with ten-digit integers. Their formation method is: first change the y in the suffix -ty of the corresponding ten-digit integer to i, and then add the suffix -eth.

4. The fourth category:

For example, thirty-first (31th) thirty-first, sixty-second (62nd) sixty-second, eighty-seventh (87th) eighty-seven, ninety-eighth (98th) ninety-eighth.

In terms of composition method, they are all changed from the cardinal word "tens", the tens digit remains unchanged, and only the cardinal word in the units position is changed into an ordinal number.

Extended information:

The main abbreviations of 1-31 ordinal words mainly have the following rules:

1. If the mantissa of the number is 1, 2, or 3 For these three numbers, 1 is followed by st (abbreviation for first), 2 is followed by nd (abbreviation for second), and 3 is followed by rd (abbreviation for third).

First, first (1st); Second, second (2nd); Third, third (3rd); Twenty-first, twenty-first (21st); Twenty-second, twenty- second (22nd); twenty-third, twenty-third (23rd).

2. Except for 1st, 2nd, and 3rd, the abbreviations of other ordinal numbers are Arabic numerals followed by th.

Fourth (4th); Sixth (6th); Eleventh (11th); Twelfth (12th); Thirteenth (13th); Fourteenth, fourteenth (14th); Fifteenth, fifteenth (15th); Twentieth, twentytieth (20th).