Step 1: Recall the common names:
Many flowers have a Hindi name that is different from the English name. 'Rajnigandha' means 'fragrance of the night'.
Step 2: Identify the flower:
The flower is Tuberose, botanical name Polianthes tuberosa.
Step 3: Why this name:
Its white, waxy flowers give a strong sweet scent, which is strongest at night. So the Hindi name stresses the night fragrance.
Step 4: Uses:
Tuberose is grown as a cut flower and loose flower. Its spikes are used in garlands, bouquets and decoration. The flowers also give an essential oil used in perfumes.
Final Answer:
Rajnigandha is the Tuberose (Polianthes tuberosa).