Diagnostic codes and what each rating level turns on. For the process itself, read the plain-English claim guides.
Nexus
The medical link between your current condition and your service. Often the single missing piece, a doctor stating your condition is "at least as likely as not" caused by service.
Service connection
Proof your condition is tied to service. Requires a current diagnosis, an in-service event, and a nexus between them.
Secondary condition
A condition caused or worsened by an already service-connected one, e.g. sleep apnea secondary to PTSD, or GERD secondary to medication.
Presumptive
A condition the VA automatically links to service for certain exposures or eras (PACT Act, Agent Orange), no nexus needed.
Pyramiding
Rating the same symptom twice under different codes. Prohibited (§4.14), but distinct residuals of one condition can be rated separately.
Prostrating
A migraine so severe you must stop all activity and lie down. The key word for DC 8100 ratings.
Combined rating
How the VA merges multiple ratings, not by adding. Each rating applies to the 'whole person' remainder (§4.25).
Bilateral factor
A 10% bonus when you have conditions in paired limbs (both knees, both legs), added before combining (§4.26).
P&T
Permanent & Total, a 100% rating with no expected improvement. No future exams, plus benefits for dependents.
TDIU
Total Disability based on Individual Unemployability, paid at the 100% rate when conditions prevent substantially gainful work, even below 100% combined.
SMC
Special Monthly Compensation, extra pay above the schedule for specific losses (SMC-K for loss of use of a creative organ, SMC-S for housebound).
DBQ
Disability Benefits Questionnaire, the standardized form examiners use to score your condition against the criteria.
C&P exam
Compensation & Pension exam, the VA appointment where an examiner evaluates your condition. Not treatment; it decides your rating.
Effective date
The date your benefits start, usually your Intent to File date. It determines your back pay.
Lay evidence
Statements from you or people who know you, describing symptoms. Real evidence when specific and consistent.
Ankylosis
A joint frozen in one position, a high-value rating criterion because it means near-total loss of motion.
CUE
Clear and Unmistakable Error, a specific type of appeal arguing the VA made a factual or legal error that changed the outcome. No time limit to file.
FDC
Fully Developed Claim, filing your claim with all evidence (medical records, STRs, statements, DBQs) attached up front. Typically processed faster.
IMO / IME
Independent Medical Opinion / Examination, a paid review by a private doctor to provide a nexus letter or DBQ to counter a negative VA C&P exam.
STRs
Service Treatment Records, your active duty medical records. The golden ticket for direct service connection.
C-File
Claims File, your entire VA record. You must submit a FOIA request to get it. Crucial for finding out exactly why you were denied or rated low.
M21-1
The Adjudication Procedures Manual, the actual instruction book VA raters must follow when deciding claims. Useful for citing rules in appeals.