SLR

In text-based chat, SLR is often used with the meaning "Sorry, Late Reply" (or "Sorry, Late Response") as a quick way to apologize for not responding to a message promptly. It helps convey politeness and recognition of the delay, offering an upfront apology for any inconvenience caused by the tardiness in responding. For example:

In photography, SLR stands for "Single-Lens Reflex." It refers to a type of camera that uses a mirror mechanism to direct light from the lens to the optical viewfinder. This allows the photographer to see exactly what the lens is capturing. When the shutter button is pressed, the mirror flips out of the way, the shutter opens, and light hits the image sensor in a digital SLR (DSLR), or film in a traditional SLR, capturing the photo. For example:

SLR is an initialism, because it’s pronounced letter by letter — "S-L-R." It's not an acronym, as they form pronounceable words (abbreviations like FANG, GOAT, NASA). In short: if you can say it like a word, it’s an acronym. If you have to spell it out, it's an initialism.