Last night, Joe dreamt of Mary. Or would it be better to say that he dreamed of her? More important: How can you know for sure?
Past participles confuse a lot of people. Take it from someone whose Boston-area in-laws opt for forms like "I should have ate" and "I could have went." When we need a verb form to go after "have," we reach for the one that sounds best. And what sounds best is whatever we're most accustomed to hearing.
Most of the time, that works out great. In any aspect of language, the most natural-sounding, most popular form is correct about 99% of the time. But the other 1% of the time, things can get ugly.
Even more important than getting past participles "right" is knowing how to make good choices. Here's a quick overview of past participles and how to look them up.
The easiest way to understand a past participle is it's the verb that goes with a form of "have." Today, he sleeps. Yesterday, he slept. In the past, he has slept. "Have" is the auxiliary verb, the helper. "Slept" is the past participle — the part that goes with "have" to express when something happened.
When you pair a past participle with a present form of "have," that tense is called the present perfect: He has eaten. When the "have" verb is in the past tense, it's the past perfect: He had eaten. The "perfect" part means the action is complete.
But how can you be sure "eaten" shouldn't be "ate"? The answer is right in front of you.
Have you ever noticed that, when you look up a verb in a dictionary, you sometimes see next to the main entry word something like, "ate, eaten, eating"? If you know how to decipher your dictionary, there's your answer.
In the front of your dictionary, under a heading like "Guide to the Dictionary" or "How to Use This Dictionary," are instructions for understanding those notations. As they explain, most dictionaries include past tense and past participle forms for irregular verbs only, not for regular verbs. That's because regular verbs like "walk" follow a simple formula. To get the simple past tense or the past participle, just add "ed." Today, he walks. Yesterday, he walked. In the past, he has walked.
But irregular verbs like "know," "dream" and "eat" don't follow that formula. For them, dictionaries have a system. Right after the entry word for an irregular verb, most dictionaries will list the past tense, followed by the past participle, followed by the progressive participle (which is the one ending in "ing").
So after "eat," you'll see "ate, eaten, eating." This tells you that "ate" is the simple past tense: Yesterday, he ate. And "eaten" is the past participle, the one that goes with "have": In the past, he has eaten.
In some cases, like "think," you'll see just one past form: "thought." This means that both the past tense and the past participle use the same form. Yesterday, he thought. In the past, he has thought.
Sometimes you see multiple options joined with the word "or." For example, after "dream" you see "dreamed or dreamt," which means both are acceptable. In this case, there's no past participle form listed, which means "dreamed" and "dreamt" are also your options for past participle.
If you're having trouble choosing, it might help to know that many publishers and media outlets have a policy of going with whichever is listed first in the dictionary. They do that mainly for consistency's sake and also because dictionaries sometimes list the most standard form first. But the choice is up to you.