Does semi acoustic and acoustic sound similar ?

Will semi acoustic sound same as acoustic even without amplifier?

Yes It will. The difference between Acoustic and Semiacoustic is like this:-

1. Acoustic is played without any Amplifier and ofcourse no electricity input required as no use of Amplifier here. Acoustics are used when we perform a small venue like a kitty party as the venue (auditorium) must be small and the sound can be reached to everyone.

2. Semi-acoustic which is Acoustic Electric Guitar is played with or without the Amplifier. Basically when we perform in front of big crowd or big venue you should go for the Semiacoustic so that the sound gets amplified and reach to all audiences. 

3. Both Acoustic and Semiacoustic give the same sound quality in general as the higher the Guitar quality gives the richer sound. And that is all upto you how much you wish to spend buying a good Guitar.

I hope I made it clear in a general way. Hope you are satisfied. I wish you a better Musicial journey. Have a good time ahead ! Thank you...

A semi-acoustic does sound similar to an acoustic guitar, but if we are getting into a discussion of tones, it all depends on the type of wood that is used in either class. Now if your gig doesn't require you to stand for long periods, it is preferable to mic up an acoustic guitar to get the purest tone from the guitar. The upside of a semi-acoustic is yes, you can plug it into an amp and jam, but if you are concerned about the tone of your guitar, then you will find that in most lower budget semi-acoustics, the pickups used won't deliver the authentic sound of the guitar. Now here's the tricky bit, you can install pickups on an acoustic guitar and turn it into a semi-acoustic. There are two ways:
1. Using a pickup across the soundhole. E.g., Fishman Rare Earth or Neo Buster.
2. Cutting a hole for a guitar Jack and screwing the pickup controls onto the side of the guitar's body similar to a semi-acoustic.

Yes! Semi acoustic and acoustic both sound same, except that semi acoustic has a pickup for amplifying the sound. However some semi acoustic guitars have a plastic back (body) which makes them sounds (no so good) (dull) without the amp.. 

So if you buy semi acoustic make sure the guitar has a good mediun sized wodden body, which will make it sound good even without the amp

There is absolutely no difference between a semi-acoustic or an acoustic guitar. They are the same thing. The only difference is that if you go for a semi-acoustic guitar you'd have an extra advantage to connect it with an amplifier, connect pedals loop stations and you can do everything that we generally do with an electric guitar.

So without connecting to an amplifier, both are exactly same. Still, when you connect it, you can use it as an electric guitar substitute (not exactly like an electric guitar, but can be used if you don't have that option or don't play electric guitar very often).