Third quarter
Lunar phase that occurs when the half of the moon is illuminated by the sun on the left side (right in the southern hemisphere). As the illuminated part is waning, it will be decreasing in size until the new moon phase. Wikipedia.
Tides
Periodic change of sea level (height) caused by the gravitational forces of the moon and sun. The moment with the lowest height is known as low tide and with the highest high tide. Time and Date / Wikipedia
Total solar eclipse
Type of solar eclipse in which the moon completely hides the solar disk. Time and Date
Transit
A time when the sun or moon is at the 180º azimuth and the maximum elevation of the day.
Tropical year
See astronomical year.
Twilight
Time period between day and night when there is still natural light, but the sun has already been hidden on the horizon. Photographically it is the period between night and blue hour, between -6º and -18º below the horizon. Astronomically it is divided into three phases; civil, nautical and astronomical twilight. Time and Date