uncommon; rare; extraordinary; matchless
unique; rare; exceptional; unparalleled; incomparable
rare; extraordinary; singular
thin (e.g. air); diluted; sparse; lacking (e.g. empathy); deficient; insufficient (e.g. zeal)
unique; rare; exceptional; unparalleled; incomparable
visitor from afar; joy-bringing spirit from the divine realms
scarcity value; rarity value; preciousness
70th birthday; ancient Greek (language)
dilute sulfuric acid; dilute sulphuric acid
rare-earth element; rare-earth metal