Vinyl:
Perfect condition, media has never been played and sleeve may have never been opened
Cassette:
Perfect condition, cassette is free of blemishes and professionally made, possibly still sealed
Vinyl:
Nearly perfect. The media has more than likely never been played, but if it has, it plays perfectly with no skipping. The sleeve is free of creases, folds, seam splits, cut-out holes, or other noticeable similar defects.
Cassette:
Sleeve is crisp and clean with only the slightest evidence of handling. Tape is likely new, free of any wear or damage.
Vinyl:
Record will show some signs that it was played and handled by a previous owner who took good care of it. Defects are of a cosmetic nature, not affecting the actual playback as a whole. Record surfaces may show some signs of wear and may have slight scuffs or very light scratches that don't affect one's listening experiences. The label may have some ring wear or discoloration, but are barely noticeable. Spindle marks may be present. Picture sleeves and inner sleeves will have some slight wear, slightly turned-up corners, or a slight seam split. An LP cover may have slight signs of wear, and may be marred by a cut-out hole, indentation, or cut corner. In general, if not for a couple of minor things wrong with it, this would be Near Mint.
Cassette:
Sleeve has slight wear, marks, indentations, and/or may possibly have a cut-out hole (or similar). Tape has been taken very good care of and may have light marks or spindle wear.
Vinyl:
Surface noise will be evident upon playing, but will not overpower the music. Groove wear is noticeable. Labels may be marred by writing, or have tape or stickers (or their residue) attached. The same will be true of picture sleeves or LP covers.
Cassette:
Sleeve contains more wear, marks, and/or indentations than a VG+. May have slight fading, a small tear/rip, or some writing. Shell may have heavier marks and wear than VG including plastic discoloration. Should play with some stronger hiss or degradation, but not enough to overpower music.
Vinyl:
Media can be played through without skipping, but it will have significant surface noise, scratches, and visible groove wear. The cover or sleeve will have seam splits, especially at the bottom or on the spine. Tape, writing, ring wear, or other defects will be present. While the record will be playable without skipping, noticeable surface noise and "ticks" will almost certainly accompany the playback.
Cassette:
Sleeve will be well worn, marked, and contain obvious indentations, fading, and/or writing, more so than a VG grade - possibly a more significant tear/rip. Tape will have heavy wear on shell. Felt stopper may be missing. Tape may have minor creasing, but not broken, and it may have heavier degradation that will overpower music.
Vinyl:
Media can be played through without skipping, but the surface noise will be more noticeable than a G+ record. It will have significant surface noise, scratches, and visible groove wear. A cover or sleeve will have seam splits. Tape, writing, ring wear, or other defects will be present.
Cassette:
Sleeve will be well worn, marked, and contain obvious indentations, fading, and/or writing, more so than a VG grade - possibly a more significant tear/rip. Tape will have heavy wear on shell. Felt stopper may be missing. Tape may have minor creasing, but not broken.
Vinyl:
The record is cracked, badly warped, and won't play through without skipping or repeating. The picture sleeve is water damaged, split on all three seams and heavily marred by wear and writing. The LP cover barely keeps the LP inside it. Inner sleeves are fully split, crinkled, and written upon.
Cassette:
Sleeve will be torn, heavily stained, showing general heavy damage, or will be partially missing. Tape will be heavily damaged, showing complete fading on the face, crinkled tape, missing screws or teeth, staining, and other heavy wear. Cassette will more than likely not play through.
Full descriptions at Discogs.com