Below are the terms understood by the VARTOOLS analytic expression evaluator

Operators:

a+b        - Addition
a-b        - Subtraction
a*b        - Multiplication
a/b        - Division
a%b        - Floating point remainder (fmod function in C)
a^b        - Exponentiation
a>b        - Greater than comparison
a>=b       - Greater than or equal to comparison
a<b        - Less than comparison
a<=b       - Less than or equal to comparison
a==b       - Logical equals
a!=b       - Logical not equal
a&&b       - Logical "and" comparison
a||b       - Logical "or" comparison
!a         - Logical "not"

Functions:

exp(x)     - exponential of x
log(x)     - natural logarithm of x
log10(x)   - base 10 logarithm of x.
sqrt(x)    - square root of x.
abs(x)     - absolute value of x.
max(x,y)   - the larger of x or y
min(x,y)   - the smaller of x or y
hypot(x,y) - sqrt(x*x+y*y)
sin(x)     - trigonometric sine of x; input in radians
cos(x)     - trigonometric cosine of x; input in radians
tan(x)     - trigonometric tangent of x; input in radians
sindegr(x) - trigonometric sine of x; input in degrees
cosdegr(x) - trigonometric cosine of x; input in degrees
tandegr(x) - trigonometric tangent of x; input in degrees
asin(x)    - inverse sine of x; output in radians
acos(x)    - inverse cosine of x; output in radians
atan2(y,x) - 4 quadrant inverse tangent of y/x; output in radians
asindegr(x) - inverse sine of x; output in degrees
acosdegr(x) - inverse cosine of x; output in degrees
atan2degr(y,x) - 4 quadrant inverse tangent of y/x; output in degrees
sinh(x)    - hyperbolic sine of x
cosh(x)    - hyperbolic cosine of x
tanh(x)    - hyperbolic tangent of x
asinh(x)   - inverse hyperbolic sine of x
acosh(x)   - inverse hyperbolic cosine of x
atanh(x)   - inverse hyperbolic tangent of x
erf(x)     - error function of x
erfc(x)    - complimentary error function of x
gamma(x)   - gamma function of x
lgamma(x)  - natural logarithm of the gamma function of x
theta(x)   - 1 for x >= 0, 0 for x < 0
round(x)   - round x to the nearest integer
ceil(x)    - smallest integer that is >= x
floor(x)   - largest integer that is <= x
rand()     - random number drawn from a uniform distribution between 0 and 1
gauss()    - random number drawn from a normal distribution with 0 mean and unit variance

Constants:

pi
e

Special Variables:

NR         - image index in the light curve starting from 0
NF         - light curve index starting from 0

Functions in the "astrofuncs" library: to use these functions include "-F astrofuncs" in your call to VARTOOLS.

EccentricAnomaly(M,e)         - returns the eccentric anomaly in radians
M         - mean anomaly in radians
e         - eccentricity
MeanAnomaly(dt,P) - returns the mean anomaly in radians
dt        - time since periastron
P         - orbital period
MeanAnomalyConjunction(dt,P,e,omega) - returns the mean anomaly in radians
dt        - time since conjunction (or transit)
P         - orbital period
e         - eccentricity
omega     - argument of periastron in degrees
TransitQuadLD(dt,P,b,Rp/R*,a/R*,e,omega,u1,u2) - returns the relative flux of a source in transit using the Mandel & Agol 2002 semi-analytic transit model for quadratic limb darkening. A value of 1 is returned for out-of-transit observations, and a value less than 1 will be returned for in-transit observations.
dt        - time since transit
P         - orbital period
b         - impact parameter at conjunction normalized to the stellar radius
Rp/R*     - planet to stellar radius ratio
a/R*      - semi-major axis in units of the stellar radius
e         - eccentricity
omega     - argument of periastron in degrees
u1        - first quadratic limb darkening coefficient
u2        - second quadratic limb darkening coefficient
TransitNonlinLD(dt,P,b,Rp/R*,a/R*,e,omega,a1,a2,a3,a4) - returns the relative flux of a source in transit using the Mandel & Agol 2002 semi-analytic transit model for a 4 parmeter non-linear limb darkening law. A value of 1 is returned for out-of-transit observations, and a value less than 1 will be returned for in-transit observations.
dt        - time since transit
P         - orbital period
b         - impact parameter at conjunction normalized to the stellar radius
Rp/R*     - planet to stellar radius ratio
a/R*      - semi-major axis in units of the stellar radius
e         - eccentricity
omega     - argument of periastron in degrees
a1        - first limb darkening coefficient
a2        - second limb darkening coefficient
a3        - third limb darkening coefficient
a4        - fourth limb darkening coefficient
BroadeningProfile(delv,dt,P,lambda,vsini,b,Rp/R*,a/R*,e,omega,u1,u2) - returns the (distorted) line broadening function at a given wavelength for a star with a transiting planet.
delv      - (wl - wl0)*c_light/wl0, where wl is the wavelength to return the broadening function at,
            wl0 is the central wavelength of the line, and c_light is the speed of light in km/s.
dt        - time since transit
P         - orbital period
lambda    - projected obliquity angle in degrees
vsini     - projected equatorial rotation velocity of the star, in km/s
b         - impact parameter at conjunction normalized to the stellar radius
Rp/R*     - planet to stellar radius ratio
a/R*      - semi-major axis in units of the stellar radius
e         - eccentricity
omega     - argument of periastron in degrees
u1        - first quadratic limb darkening coefficient
u2        - second quadratic limb darkening coefficient
TransitProjectedX(dt,P,lambda,b,Rp/R*,a/R*,e,omega) - returns the sky-projected X position of the center of a planet in its orbit in front of the star, in units of the stellar radius. The coordinate system used has the rotation axis of the star along the Y direction.
dt        - time since transit
P         - orbital period
lambda    - sky-projected obliquity angle in degrees
b         - impact parameter at conjunction normalized to the stellar radius
Rp/R*     - planet to stellar radius ratio
a/R*      - semi-major axis in units of the stellar radius
e         - eccentricity
omega     - argument of periastron in degrees
TransitProjectedY(dt,P,lambda,b,Rp/R*,a/R*,e,omega) - returns the sky-projected Y position of the center of a planet in its orbit in front of the star, in units of the stellar radius. The coordinate system used has the rotation axis of the star along the Y direction.
dt        - time since transit
P         - orbital period
lambda    - sky-projected obliquity angle in degrees
b         - impact parameter at conjunction normalized to the stellar radius
Rp/R*     - planet to stellar radius ratio
a/R*      - semi-major axis in units of the stellar radius
e         - eccentricity
omega     - argument of periastron in degrees
RV_E(E,e,omega,K) - returns the radial velocity of an object on a Keplerian orbit given the mean anomaly as the input time unit. The radial velocity will be in the same units as K.
M         - mean anomaly in radians
e         - eccentricity
omega     - argument of periastron in degrees
K         - RV semi-amplitude
RV_dt(E,e,omega,K) - returns the radial velocity of an object on a Keplerian orbit given the time from conjection of its companion as the input time unit (e.g., this is the radial velocity of a transiting planet host star given the time since transit). The radial velocity will be in the same units as K.
dt        - time from conjunction
P         - orbital period
e         - eccentricity
omega     - argument of periastron in degrees
K         - RV semi-amplitude
RV_dtp(E,e,omega,K) - returns the radial velocity of an object on a Keplerian orbit given the time from periastron as the input time unit. The radial velocity will be in the same units as K.
dt        - time from periastron
P         - orbital period
e         - eccentricity
omega     - argument of periastron in degrees
K         - RV semi-amplitude