This verb follows the standard English past tense rule: simply add -ed to the base form.
Subjoin is regular. It follows the Standard -ed rule.
Use past time markers: "Yesterday, she subjoined to the store."
No. Use "did not subjoin" (not "did not subjoined").
The verb subjoin follows the standard English past tense conjugation rule. When forming the past tense, subjoin becomes subjoined. This follows the Standard -ed pattern, which is one of the most common conjugation rules in English.
Understanding why subjoin becomes subjoined helps with spelling and pronunciation. This verb follows the standard English past tense rule: simply add -ed to the base form.
When using subjoined 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 subjoined to the store." The past tense form does not change based on the subject — I subjoined, you subjoined, he/she subjoined, we subjoined, they subjoined.