Where does the adjective form extensible come from and does it connote anything different than extendible? What's the difference, if any, between the two?
It appears that I probably draw a finer distinction here than others may, but the good thing is that for those that say the two are interchangeable, my usage will seem unremarkable, and for those that care, my usage will seem consistent.
I use extendable in cases where it means the opposite of retractable. In other words, a telescoping wand is extendable, the legs of my camera tripod are extendable.
I use extensible when I mean that the functionality of something may be increased or enhanced by the addition of an extension- an add-on module or component. My web browser is extensible because I can add an Adobe Flash extension which allows me to view flash content. I think it would sound a bit odd to talk about my web-browser being extendable.
There are lots and lots of these. They usually came to us that way straight from Latin, and seldom mean anything different from each other. One may be more rare than another, though.
- comprehendible, comprehensible
- corrodable, corrodible, corrosible
- defendable, defensible
- deridable, derisible
- dividable, divisible
- evadable, evasible
- expandable, expansible
- explodable, explosible
- extendible, extensible
- inevadible, inevasible
- invadable, invasible
- offendable, offensible
- persuadable, persuasible
- protrudable, protrusible
- reprehendable, reprehensible
- rescindable, rescindible
- revisable, revisible
- subdividable, subdivisible
- suspendible, suspensible
- undefendable, undefensible
- undividable, undivisible
The Oxford Dictionary of American Usage and Style (2000) says:
Other variant adjectives, though, are merely duplicative. Typical examples are extendable, extendible, and extensible. The first of these is now prevalent in AmE (though labeled obsolete in the OED). Extensible was, through the mid-20th century, the most common form, but today it trails extendable by a substantial margin, while extendible continues to appear infrequently. Writers and editors ought to settle on the most firmly established form--extendable, which is as well formed as the variants--and trouble their minds with weightier matters.
In WordReference site, its given that extensible means capable of being extended.
1 make larger or longer in space or time.
• occupy a specified area or continue for a specified distance.
2 hold (something) out towards someone.
• offer or make available.
3 (extend to) be applicable to.
4 strain or exert to the utmost.
Also want to add some info got from another useful source,
Extensible seems to me to indicate stretchability whereas extendable suggests an opening out or lengthening. An elastic band is extensible, i.e.: it can be stretched, whereas my lunch hour is extendable, i.e.: it can be added to, but an hour is an hour and cannot be stretched. There is also extensile which seems to mean the same as extensible.