Perceptible, sensible, palpable, tangible, appreciable, ponderable all mean capable of being apprehended through the senses or intellect as real and existent.
Perceptible may be used inclusively to describe whatever comes within the range of one's senses and can be recognized in itself or by certain signs.
It may also be used with or without qualification (as by just, scarcely, or barely ) to describe something that just passes a borderline (as that between invisibility and visibility or inaudibility and audibility).
Sensible (see also MATERIAL AWARE ) may be used to describe whatever is clearly apprehended through the bodily senses or which impresses itself strongly on the mind through the medium of sensations. In contrast with perceptible, however, sensible applies to what is more obvious, even sometimes to what is patent through its effects or signs; thus, a sensible change in tone is one which is immediately recognized; a sensible difference in a person's expression is one which is quickly detected.
Both palpable and tangible in their primary senses may be used to describe anything which is perceptible through the sense of touch.
Palpable, however, although it is used of what is felt by touching with the tips of the fingers, as often implies a sensation produced as a sensation sought and therefore may be applied to whatever evokes a response from tactile receptors in any part of the body,
Tangible, on the other hand, is applied primarily to things which may be or are handled or grasped.
In their secondary senses these two words diverge widely. Palpable, in one of its most common meanings, implies a high degree of perceptibility (see under EVIDENT ); in poetic use, especially when applied to an immaterial thing, it suggests an almost physical awareness of its existence or reality.
Tangible in its extended senses is applied to things that can be thought of as having real, independent, or objective existence whether they are apparent to the senses or not or whether they can be handled or not; thus, tangible ideas are those that can be grasped by the mind and made objects of thought; tangible advantages are those having a substantial character; tangible assets are those (as equipment and inventory) that can be appraised with reasonable accuracy as distinguished from those (as goodwill) that are intangible.
Appreciable is applicable to whatever is large enough to be measured, weighed, valued, or otherwise estimated; thus, a perceptible change in the temperature may be so slight a change that it almost but not quite escapes notice; a palpable change in temperature may still be slight, but it is great enough to make it definitely felt; an appreciable change in temperature may also be slight, but its extent is determinable by reference to a thermometer. But appreciable may lose any clear notion of measurability and then often approaches considerable or significant in meaning.
Ponderable is applicable to whatever can be weighed either physically or mentally. The word tends, however, to be applied to what is appreciable in terms of weight or significance as distinguished from what is so intangible as to elude such determination.