1. 能否右键使用：special: 无用; | useable: 能否右键使用; | dropsound: 掉下时的音效;

1. convenient for use or disposal

    e.g. the house is available after July 1
           2000 square feet of usable office space

    Synonym: availableusable

2. fit or ready for use or service

    e.g. the toaster was still functional even after being dropped
           the lawnmower is a bit rusty but still usable
           an operational aircraft
           the dishwasher is now in working order

    Synonym: functionalusableoperableoperational

3. capable of being put to use

    e.g. usable byproducts

    Synonym: usable