A RAM module has gone out on your laptop and requires replacement. Without opening the laptop up or possessing any additional knowledge about your system, you know that you will most likely need to replace the module with a ______ type module.
Laptop and mobile devices typically utilize SO-DIMM type RAM modules, as these modules are smaller in form factor than typical DIMM modules.
While DDR 3 or DDR 4 could be an answer, this would require more detailed information about the motherboard on your system.
If you got this one right, you're not SO DIMM.
(Sorry for the pun; I couldn't help myself)
A SO-DIMM (pronounced "so-dimm" , also spelled "SODIMM") or small outline DIMM, is a type of computer memory built using integrated circuits. A SO-DIMM is a smaller alternative to a DIMM, being roughly half the physical size of a regular DIMM.
SO-DIMMs are often used in systems that have limited space, which include laptops, notebooks, small-footprint personal computers such as those based on Nano-ITX motherboards, high-end upgradable office printers, and networking hardware such as routers and NAS devices. They are usually available with the same size data path and speed ratings of the regular DIMMs though normally with smaller capacities.