6.1.1  Identifiers and Keywords

POV-Ray allows you to define identifiers for later use in the scene file. An identifier may be 1 to 40 characters long. It may consist of upper and lower case letters, the digits 0 through 9 or an underscore character ("_"). the first character must be an alphabetic character. The declaration of identifiers is covered later.

POV-Ray has a number of reserved keywords which are listed below.

a
aa_level aa_threshold abs absorption accuracy acos acosh adaptive adc_bailout agate agate_turb all	all_intersections alpha altitude always_sample ambient ambient_light angle aperture append arc_angle area_light array	asc ascii asin asinh assumed_gamma atan atan2 atanh autostop average
b
b_spline background bezier_spline bicubic_patch black_hole blob blue	blur_samples bounded_by box boxed bozo break brick	brick_size brightness brilliance bump_map bump_size bumps
c
camera case caustics ceil cells charset checker chr circular clipped_by clock clock_delta clock_on collect	color color_map colour colour_map component composite concat cone confidence conic_sweep conserve_energy contained_by control0 control1	coords cos cosh count crackle crand cube cubic cubic_spline cubic_wave cutaway_textures cylinder cylindrical
d
debug declare default defined degrees density density_file density_map	dents df3 difference diffuse dimension_size dimensions direction disc	dispersion dispersion_samples dist_exp distance div double_illuminate
e
eccentricity else emission end	error error_bound evaluate exp	expand_thresholds exponent exterior extinction
f
face_indices facets fade_color fade_colour fade_distance fade_power falloff falloff_angle false fclose	file_exists filter final_clock final_frame finish fisheye flatness flip floor focal_point	fog fog_alt fog_offset fog_type fopen form frame_number frequency fresnel function
g
gather gif global_lights	global_settings gradient granite	gray gray_threshold green
h
height_field hexagon	hf_gray_16 hierarchy	hypercomplex hollow
i
if ifdef iff ifndef image_height image_map image_pattern image_width include	initial_clock initial_frame inside inside_vector int interior interior_texture internal interpolate	intersection intervals inverse ior irid irid_wavelength isosurface
j
jitter jpeg	julia julia_fractal
l
lambda lathe leopard light_group light_source	linear_spline linear_sweep ln load_file local	location log look_at looks_like low_error_factor
m
macro magnet major_radius mandel map_type marble material material_map matrix max max_extent	max_gradient max_intersections max_iteration max_sample max_trace max_trace_level media media_attenuation media_interaction merge mesh	mesh2 metallic method metric min min_extent minimum_reuse mod mortar
n
natural_spline nearest_count no no_bump_scale no_image	no_reflection no_shadow noise_generator normal normal_indices	normal_map normal_vectors number_of_waves
o
object octaves off offset omega	omnimax on once onion open	orient orientation orthographic
p
panoramic parallel parametric pass_through pattern perspective pgm phase phong phong_size photons	pi pigment pigment_map pigment_pattern planar plane png point_at poly poly_wave polygon	pot pow ppm precision precompute pretrace_end pretrace_start prism prod projected_through pwr
q
quadratic_spline quadric quartic	quaternion quick_color quick_colour	quilted
r
radial radians radiosity radius rainbow ramp_wave rand range ratio	read reciprocal recursion_limit red reflection reflection_exponent refraction render repeat	rgb rgbf rgbft rgbt right ripples rotate roughness
s
samples save_file scale scallop_wave scattering seed select shadowless sin sine_wave sinh size sky sky_sphere slice slope	slope_map smooth smooth_triangle solid sor spacing specular sphere sphere_sweep spherical spiral1 spiral2 spline split_union spotlight spotted	sqr sqrt statistics str strcmp strength strlen strlwr strupr sturm substr sum superellipsoid switch sys
t
t tan tanh target text texture texture_list texture_map tga thickness	threshold tiff tightness tile2 tiles tolerance toroidal torus trace transform	translate transmit triangle triangle_wave true ttf turb_depth turbulence type
u
u u_steps ultra_wide_angle undef union	up use_alpha use_color use_colour use_index	utf8 uv_indices uv_mapping uv_vectors
v
v v_steps val variance vaxis_rotate	vcross vdot version vertex_vectors vlength	vnormalize vrotate vstr vturbulence
w
warning warp water_level	waves while width	wood wrinkles write
x
x
y
y	yes
z
z

All reserved words are fully lower case. Therefore it is recommended that your identifiers contain at least one upper case character so it is sure to avoid conflict with reserved words.