/ˈɒblɒŋ/
[adjective] Describing a shape that is longer than it is wide, like a rectangle that has been stretched in one direction. An oblong shape has straight sides but is not a perfect square.
The 'ob-' in oblong means 'towards' — so oblong literally means something stretching towards being long.
The word 'oblong' comes directly from the Latin word 'oblongus', which was itself built from two parts: the prefix 'ob-', meaning 'towards' or 'against', and 'longus', meaning 'long'. Together, they described something that leaned in the direction of being long — stretched, extended, pulled away from a perfect square shape. Latin 'oblongus' was a practical, geometric word, used by Roman writers to describe anything from fields and tablets to swimming pools and rooms that were noticeably longer on one side.
The word passed into English in the 15th century, most likely through learned writers and scholars who were reading classical Latin texts on geometry, architecture, and natural philosophy. Unlike many Latin words that arrived via French after the Norman Conquest, 'oblong' appears to have come more directly through scholarly Latin, the language of universities and the Church. This gives it a slightly technical, almost scientific feel that it has never quite lost.
Latin 'longus' is one of the most productive roots in the English language. It travelled through Old French as 'long', giving English the everyday word 'long' itself. But it also produced 'longitude' (via Latin 'longitudo' → English 'longitude'), 'elongate' (via Latin 'elongare' → English 'elongate'), 'prolong' (via Latin 'prolongare' → Old French 'prolonguer' → English 'prolong'), and even 'lunge', which traces back to the same root through French. The prefix 'ob-' is equally busy — it appears in words like 'obvious', 'obstacle', and 'object', always carrying a sense of something positioned in relation to something else.
Interestingly, for most of its early life in English, 'oblong' was used as both an adjective and a noun. Writers of the 16th and 17th centuries would speak of drawing 'an oblong' just as naturally as they might say 'a circle' or 'a triangle'. This noun use has faded in modern English, where 'rectangle' tends to do that job instead, though 'oblong' as a noun is still perfectly understood in British English, especially when talking to children about shapes.
The word has also carried a slightly informal, almost affectionate quality through the centuries. Where 'rectangle' sounds clinical and mathematical, 'oblong' sounds almost friendly — a little wobbly, a little imprecise. People tend to use it when they want to describe something that is roughly rectangular but not quite perfect: a misshapen biscuit, an oddly proportioned room, a face that is just a little too long. This warmth and flexibility has helped 'oblong' survive into modern English, sitting comfortably alongside its more technical cousin 'rectangle' rather than being replaced by it.