Could or Was Able?

How to use: can and be able to

Can is used to express ability (の能力) or possibility (可能性あり). It is a modal verb (法動詞) so there is no conjugation (動詞の語形変化がない).

Example 1: Can

- I can speak English.
- I can drive a car.
- He can speak English and Chinese.
- They can't come to the party.

Could is the past tense* (動詞の過去形) of can. And therefore it also is not conjugated.

*Note:

Could is almost never used in the affirmative (ほとんど肯定的に使わない) in the past tense unless talking about an ability once performed in the past.過去の一貫した能力を表す。瞬時の能力は was [were] able toになります。

Example 2: Could

- I couldn't go to work because I was sick.
- I couldn't understand what my teacher said.
- I couldn't enjoy the party.

(If speaking in the affirmative (肯定的に), we would usually use the simple past tense (単純過去時制). For example: "I called you yesterday." If you said "I couldn't call you yesterday," that would be OK, too. It sounds strange if you said "I could call you yesterday.")

Example 3: Could ? when ?

- I could play the piano when I was younger.
- I could swim across the river when I was twelve.

"Be able to" is basically another way of expressing "ability" and "possibility" in the past in the affirmative (肯定的に).

Example 4: Be Able to

- We were able to catch the ferry on time.
- They were able to give me directions.
- I was able to go on vacation during Golden Week.
- She was able to vote.

Hope this helps. Any questions or comments? Click on comments below.

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