Ti-ratana: 'Three Jewels' or Triple Gem, which by all Buddhists are revered as the most venerable things, are the Buddha, the Dhamma and the Noble Sangha.' i.e.: the Enlightened One; the law of deliverance discovered, realized and proclaimed by him; and the Community of Noble Disciples and those who live in accordance with the Law. - The contemplations of the 3 Jewels belong to the 10 contemplations.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.