Verbs ending in a consonant followed by -y change the -y to -ied in the past tense form.
Efficacy is regular. It follows the -ied Conversion rule.
Use past time markers: "Yesterday, she efficacied to the store."
No. Use "did not efficacy" (not "did not efficacied").
The verb efficacy follows the standard English past tense conjugation rule. When forming the past tense, efficacy becomes efficacied. This follows the -ied Conversion pattern, which is one of the most common conjugation rules in English.
Understanding why efficacy becomes efficacied 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 efficacied 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 efficacied to the store." The past tense form does not change based on the subject — I efficacied, you efficacied, he/she efficacied, we efficacied, they efficacied.