Meaning of the suffixes found on Intel CPUs

What is the meaning in K in i7?
Is U defined as Ultrabook in Intel CPUs?

Intel uses suffixes in their CPU product code. To help you identify the meaning of suffixes, I have gathered their meaning for everyone's reference. 





For 4th Generation (Haswell) CPUs:

Alpha Suffix	Description	Example
Desktop
K	Unlocked	Intel® Core™ i7-4770K processor
R	Desktop processor based on BGA1364 (mobile) package with high performance graphics	Intel Core i7-4770R processor
S	Performance-optimized lifestyle	Intel Core i7-4770S processor
T	Power-optimized lifestyle	Intel Core i7-4770T processor
Mobile (Notebook and Tablets)
HQ	High performance graphics	Intel® Core™ i7-4700HQ processor
MX	Mobile extreme edition	Intel Core i7-4940MX processor Extreme Edition
MQ	Quad-core mobile	Intel Core i7-4900MQ processor Intel Core i7-4702MQ processor
M	Mobile	Intel Core i7-4600M processor Intel Core i5-4300M processor
U	Ultra-low power	Intel Core i7-4550U processor
Y	Extremely low power	Intel Core i7-4610Y processor

For 3rd Generation (Ivy Bridge) CPUs:
              

Alpha Suffix	Description	Example
Desktop
K	Unlocked	Intel® Core™ i7-3370K processor Intel Core i5-3570K processor
S	Performance-optimized lifestyle	Intel Core i7-3770S processor Intel Core i5-3550S processor
T	Power-optimized lifestyle	Intel Core i7-3770T processor Intel Core i5-3570T processor
Mobile
M	Mobile	Intel® Core™ i7-3520M processor
QM	Quad-core mobile	Intel Core i7-3820QM processor
U	Ultra-low power	Intel Core i7-3667U processor
Y	Extremely low power	Intel Core i7-3689Y processor

 For 2nd Generation (Sandy Bridge) CPUs:
 

Alpha Suffix	Description	Example
Desktop
K	Unlocked	Intel® Core™ i7-2600K processor Intel Core i5-2500K processor
S	Performance-optimized lifestyle	Intel Core i5-2500S processor Intel Core i5-2400S processor
T	Power-optimized lifestyle	Intel Core i5-2500T processor Intel Core i5-2390T processor
Mobile
M	Mobile	Intel® Core™ i7-2677M processor
QM	Quad-core mobile	Intel Core i7-2860QM processor

  For 1stGeneration (Nehalem) CPUs:

 Processor numbers for the previous generation Intel Core processor family have an alpha/numerical identifier followed by a three-digit numerical sequence.

Processor numbers for the Intel® Core™2 processor family brands are categorized with an alpha prefix followed by a four-digit numerical sequence. The table below explains the alpha prefixes used for the Intel Core 2 processor family.

Alpha Prefix	Description
QX	Desktop or mobile quad-core extreme performance processors
X	Desktop or mobile dual-core extreme performance processors
Q	Mobile quad-core high performance processors
E	Desktop energy efficient dual-core processors with TDP greater than or equal to 55 W
T	Mobile highly energy efficient processors with TDP 30-39 W
P	Mobile highly energy efficient processor with TDP 20-29 W
L	Mobile highly energy efficient with TDP 12-19 W
U	Mobile ultra high energy efficient with TDP less than or equal to 11.9 W
S	Mobile small form-factor with 22x22 BGA package

  For Previous Generation CPUs:

Processor numbers for the Intel® Core™2 Quad family have an alpha prefix followed by a four-digit numerical sequence. Additionally, low power Intel Core 2 Quad processors are identifiable by an "S" suffix, which represents processors having a lower thermal design power.

Intel® Atom™ processors

Processor numbers for the Intel® Atom™ processor family are categorized by a three-digit numerical sequence. Netbook class Intel® Atom™ processors have an alpha prefix of N, and Intel Atom processors with an alpha prefix of Z indicate the processor is for Mobile Internet Devices (MIDs).
A higher number within a processor class or family generally indicates more features. A higher processor number may have more of one feature and less of another.

             

Intel® Pentium® processors

Processor numbers for the Intel Pentium brand have an alpha prefix followed by a four-character numerical sequence. All are desktop energy-efficient dual-core processors with TDP that is greater than or equal to 65 W.
A higher number within a processor class or family generally indicates more features such as cache, clock speed, Front Side Bus or other Intel technologies.¹ A higher number processor may also have more of one feature and less of another.

Intel® Celeron® processors

Processor numbers for the Intel® Celeron® brand are expressed with either a three-digit numerical sequence or a five-character sequence with an alphabetical prefix and four digits, depending on the processor type.
A higher number within a processor class or family generally indicates more features such as cache, clock speed, Front Side Bus or other Intel technologies.¹ A higher number processor may also have more of one feature and less of another.

Alpha Suffix	Description	Example
Desktop
K	Unlocked	Intel® Core™ i7-2600K processor Intel Core i5-2500K processor
S	Performance-optimized lifestyle	Intel Core i5-2500S processor Intel Core i5-2400S processor
T	Power-optimized lifestyle	Intel Core i5-2500T processor Intel Core i5-2390T processor
Mobile
M	Mobile	Intel® Core™ i7-2677M processor
QM	Quad-core mobile	Intel Core i7-2860QM processor

Processor numbers for the previous generation Intel Core processor family have an alpha/numerical identifier followed by a three-digit numerical sequence.

Processor numbers for the Intel® Core™2 processor family brands are categorized with an alpha prefix followed by a four-digit numerical sequence. The table below explains the alpha prefixes used for the Intel Core 2 processor family.

Alpha Prefix	Description
QX	Desktop or mobile quad-core extreme performance processors
X	Desktop or mobile dual-core extreme performance processors
Q	Mobile quad-core high performance processors
E	Desktop energy efficient dual-core processors with TDP greater than or equal to 55 W
T	Mobile highly energy efficient processors with TDP 30-39 W
P	Mobile highly energy efficient processor with TDP 20-29 W
L	Mobile highly energy efficient with TDP 12-19 W
U	Mobile ultra high energy efficient with TDP less than or equal to 11.9 W
S	Mobile small form-factor with 22x22 BGA package

Processor numbers for the Intel® Core™2 Quad family have an alpha prefix followed by a four-digit numerical sequence. Additionally, low power Intel Core 2 Quad processors are identifiable by an "S" suffix, which represents processors having a lower thermal design power.

Intel® Atom™ processors

Processor numbers for the Intel® Atom™ processor family are categorized by a three-digit numerical sequence. Netbook class Intel® Atom™ processors have an alpha prefix of N, and Intel Atom processors with an alpha prefix of Z indicate the processor is for Mobile Internet Devices (MIDs).
A higher number within a processor class or family generally indicates more features. A higher processor number may have more of one feature and less of another.

             

Intel® Pentium® processors

Processor numbers for the Intel Pentium brand have an alpha prefix followed by a four-character numerical sequence. All are desktop energy-efficient dual-core processors with TDP that is greater than or equal to 65 W.
A higher number within a processor class or family generally indicates more features such as cache, clock speed, Front Side Bus or other Intel technologies.¹ A higher number processor may also have more of one feature and less of another.

Intel® Celeron® processors

Processor numbers for the Intel® Celeron® brand are expressed with either a three-digit numerical sequence or a five-character sequence with an alphabetical prefix and four digits, depending on the processor type.
A higher number within a processor class or family generally indicates more features such as cache, clock speed, Front Side Bus or other Intel technologies.¹ A higher number processor may also have more of one feature and less of another.

source: About Intel Processors