declīnˈable adjective (grammar)

Having different inflections according to the case

declīˈnal adjective

Bending downwards

declinant /dekˈlin-ənt/ adjective (heraldry)

Having the tail hanging down

decˈlinate adjective (botany)

Curving downwards

declināˈtion noun

1. Act of declining (US)
2. A sloping or bending downwards
3. Deviation
4. The angular distance of a heavenly body from the celestial equator (astronomy)

decˈlinātor noun

An instrument determining declination

declīnˈatory adjective

Containing a declination or refusal

declīnˈature noun

1. Act of declining or refusing
2. A plea declining the jurisdiction of a judge (law)

declinomˈeter noun

An instrument for measuring declination in various senses, esp the declination of the compass or magnetic declination (ie the deviation of the magnetic needle from the true north), or the declination or dip of a compass needle (see dip of the needle under dip)

on the decline

In the process of becoming less, deteriorating