一次了解【數字英文單字】基數|序數 – 英語學習筆記-Cardinal, Ordinal Numbers

數字有分為「基數」Cardinal numbers 和「序數」Ordinal numbers這兩類
・基數：表示事物的數量，像是(1)one, (2)two, (3)three ..等
・序數：是指排順序的數字，像是(第一)first, (第二)second, (第三)third..等

基數 | 序數 中英對照表

基數	Cardinal numbers	序數	Ordinal numbers
1	one	1st	first
2	two	2nd	second
3	three	3rd	third
4	four	4th	fourth
5	five	5th	fifth
6	six	6th	sixth
7	seven	7th	seventh
8	eight	8th	eighth
9	nine	9th	ninth
10	ten	10th	tenth
11	eleven	11th	eleventh
12	twelve	12th	twelfth
13	thirteen	13th	thirteenth
14	fourteen	14th	fourteenth
15	fifteen	15th	fifteenth
16	sixteen	16th	sixteenth
17	seventeen	17th	seventeenth
18	eighteen	18th	eighteenth
19	nineteen	19th	nineteenth
20	twenty	20th	twentieth
21	twenty-one	21st	twenty-first
22	twenty-two	22nd	twenty-second
23	twenty-three	23rd	twenty-third
24	twenty-four	24th	twenty-fourth
25	twenty-five	25th	twenty-fifth
26	twenty-six	26th	twenty-sixth
27	twenty-seven	27th	twenty-seventh
28	twenty-eight	28th	twenty-eighth
29	twenty-nine	29th	twenty-ninth
30	thirty	30th	thirtieth

1th和 1st 的差別在哪裡？哪個正確？

For numbers ending in 1, 2 and 3, (except 11, 12, 13)
1 – first (1st)
2 – second (2nd)
3 – third (3rd)

從上表可知道1″st”才是正確的，是從first縮寫而成，所以不使用1th 而是使用1st。21, 31, 41..後面尾數是1的，序數縮寫都需要改成”st”, e.g., 21st , 31st, 41st and so on.
(但特別注意的是11的英文單字是eleventh縮寫是11″th”，如果寫成11″st”就錯囉。)

31	thirty-one	31st	thirty-first
32	thirty-two	32nd	thirty-second
33	thirty-three	33rd	thirty-third
34	thirty-four	34th	thirty-fourth
35	thirty-five	35th	thirty-fifth
36	thiry-six	36th	thirty-sixth
37	thirty-seven	37th	thirty-seventh
38	thirty-eight	38th	thirty-eighth
39	thirty-nine	39th	thirty-nine
40	forty	40th	fortieth
41	forty-one	41st	forty-first
42	forty-two	42nd	forty-second
43	forty-three	43rd	forty-third
44	forty-four	44th	forty-fourth
45	forty-five	45th	forty-fifth
46	forty-six	46th	forty-sixth
47	forty-seven	47th	forty-seventh
48	forty-eight	48th	forty-eighth
49	forty-nine	49th	forty-ninth
50	fifty	50th	fiftieth
51	fifty-one	51st	fifty-first
52	fifty-two	52nd	fifty-second
53	fifty-three	53rd	fifty-third
54	fifty-four	54th	fifty-fourth
55	fifty-five	55th	fifty-fifth
56	fifty-six	56th	fifty-sixth
57	fifty-seven	57th	fifty-seventh
58	fifty-eight	58th	fifty-eighth
59	fifty-nine	59th	fifty-ninth
60	sixty	60th	sixtieth
61	sixty-one	61st	sixty-first
62	sixty-two	62nd	sixty-second
63	sixty-three	63rd	sixty-third
64	sixty-four	64th	sixty-fourth
65	sixty-five	65th	sixty-fifth
66	sixty-six	66th	sixty-sixth
67	sixty-seven	67th	sixty-seventh
68	sixty-eight	68th	sixty-eighth
69	sixty-nine	69th	sixty-ninth
70	seventy	70th	seventieth
71	seventy-one	71st	seventy-first
72	seventy-two	72nd	seventy-second
73	seventy-three	73rd	seventy-third
74	seventy-four	74th	seventy-fourth
75	seventy-five	75th	seventy-fifth
76	seventy-six	76th	seventy-sixth
77	seventy-seven	77th	seventy-seventh
78	seventy-eight	78th	seventy-eighth
79	seventy-nine	79th	seventy-ninth
80	eighty	80th	eightieth
81	eighty-one	81st	eighty-first
82	eighty-two	82nd	eighty-second
83	eighty-three	83rd	eighty-third
84	eighty-four	84th	eighty-fourth
85	eighty-five	85th	eighty-fifth
86	eighty-six	86th	eighty-sixth
87	eighty-seven	87th	eighty-seventh
88	eighty-eight	88th	eighty-eighth
89	eighty-nine	89th	eighty-nine
90	ninety	90th	ninetieth
91	ninety-one	91st	ninety-first
92	ninety-two	92nd	ninety-second
93	ninety-three	93rd	ninety-third
94	ninety-four	94th	ninety-fourth
95	ninety-five	95th	ninety-fifth
96	ninety-six	96th	ninety-sixth
97	ninety-seven	97th	ninety-seventh
98	ninety-eight	98th	ninety-eighth
99	ninety-nine	99th	ninety-ninth
100	hundred	100th	hundredth

數字的英文規則

When we say the days of the month, we put -th at the end of the number.
4 – fourth (4th)
11 – eleventh (11th)
26 – twenty-sixth (26th)

• 從4 – 19，在基數的字尾加-th (six -> sixth)
• 字尾有-ve的，去-ve 加 -fth (five -> fifth)
• 字尾有-e的，去-e 加 -th (nine -> ninth)
• 字尾有-ty的，去-y加 -ieth (thirt -> thirtieth)

基數	Cardinal numbers	序數	Ordinal numbers
10	ten	10th	tenth
20	twenty	20th	twentieth
30	thirty	30th	thirtieth
40	forty	40th	fortieth
50	fifty	50th	fiftieth
60	sixty	60th	sixtieth
70	seventy	70th	seventieth
80	eighty	80th	eightieth
90	ninety	90th	ninetieth
100	hundred	100th	hundredth
1000	thousand	1000th	thousandth

除了11-20有特定的英文單字以外，其餘21開始的個位數加上序數即可。

• 31st：thirty-first
• 55th：fifty-fifth
• 68th：sixty-eighth

序數的縮寫：「數字＋字尾兩位英文字母」 e.g., first, 1st (可直接對照上面“序數”欄位)

100th 可以使用 hundredth 或 one hundredth
1000th 也可以使用 thousandth 或 one thousandth

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