Why don't you research that? Seriously, just because you can't google an answer in 30 seconds does not mean the various definitions are nonexistent.

@bugsmetoo

thank you for your comment. Actually lately i've been reading books on spaces and degree of enclosure but there is no specific defination on semi open spaces. 

 "semi" is a variable term and material selection is irrelevant to whether or not a space is considered "semi"-open.

Done, thesis finished. A+

@non sequitur

well here i would like to take an example, like if we take a veranda closed from three sides with vertical u-shaped planes, and suppose there is also a sitting provision of about 60cm from the ground on the open side and is also fully grilled for security reasons. so will it still be a semi-open?

...sure why not. Call it an semi-enclosed urban garden if you like, you're not labelling a product for specification purposes. I don't think you understand the semantic problems inherent in your "thesis" position.

yaah actually that's what i wanted to know when will a space be semi-open and when it will be converted to semi-closed space. basically it's all dependent on ones perception but can we categories them with the help of any quantitative terminology.

No. There is beauty in leaving things vague and irrational. Not everything needs to be rationalized to death.

leave the quantitative thinking to engineers. They need something to do until they are all replaced by robots.