Can you say Dekiba

Question

Can you say Dekiba as in Dekiru (to do) + ば　(the suffix for 'be able to do'), so that dekiba becomes 'if you are able to'?

Answer 1

The short answer

No, you can't say dekiba. Or rather, you could indeed say that, but it's not correct and folks might not catch your intended meaning. :)

The long answer

Dekiru is a so-called "type-2" or "vowel-stem" verb, where the stem of the vowel (the part that doesn't change when conjugating the different forms) ends in a vowel: dekiru → dekinai, dekite, dekimasu, etc. This is basically the same kind of verb as taberu "to eat" → taberu, tabenai, tabete, tabemasu, etc.

Other verbs are called "type-1" or "consonant-stem" verbs, where the stem ends in a consonant. A common one you might already know is kiku "to hear, to listen": kiku → kikanai, kiite (contracted from older kikite), kikimasu, etc.

The -ba conditional ending requires a special -e- ending on the verb stem, in addition to any -e that's already there. For consonant-stem verbs like kiku, you just take the stem kik-, add -e and then the -ba: kikeba. For vowel-stem verbs like dekiru or taberu, you need to add -re as a special kind of stub mora (a mora is kind of like a syllable, but it's about the rhythm and time it takes to say a word -- this is very important in Japanese, with its long vowels and geminate (doubled) consonants -- see https://en.wikipedia.org/wiki/Mora_(linguistics)). So for taberu, you'd take the stem tabe-, add that -re, and then add the -ba: tabereba. Same for dekiru, as deki- + -re + -ba: dekireba.