Verbs ending in a consonant followed by -y change the -y to -ied in the past tense form.
Co-vary is regular. It follows the -ied Conversion rule.
Use past time markers: "Yesterday, she co-varied to the store."
No. Use "did not co-vary" (not "did not co-varied").
The verb co-vary follows the standard English past tense conjugation rule. When forming the past tense, co-vary becomes co-varied. This follows the -ied Conversion pattern, which is one of the most common conjugation rules in English.
Understanding why co-vary becomes co-varied helps with spelling and pronunciation. Verbs ending in a consonant followed by -y change the -y to -ied in the past tense form.
When using co-varied in writing, remember that it functions as a past tense verb and typically appears with time markers like yesterday, last week, or ago. For example: "Yesterday, she co-varied to the store." The past tense form does not change based on the subject — I co-varied, you co-varied, he/she co-varied, we co-varied, they co-varied.