Learn Spanish (Latin America): El modelo nuevo no es tan práctico como el viejo. - The new model is not as practical as the old one.

To say that two things are equal in some way, Spanish uses the pattern tan + [adjective] + como. Here, the first "as" is tan and the second "as" is como. So, tan práctico como translates exactly to "as practical as".

Does the adjective práctico need to match the noun it describes?

Yes! Even though it sits inside the tan ... como structure, práctico is still describing the subject, el modelo. Because modelo is masculine and singular, the adjective must also be masculine and singular. If we were comparing something feminine, like a new camera (la cámara nueva), it would change to tan práctica como.

Where is the word for "one" in el viejo (the old one)?

Spanish doesn't use a word for "one" in these situations. To avoid repeating the noun (saying "the old model" again), you can just use the word for "the" (el) directly in front of the adjective (viejo). El viejo literally means "the old", but in English we naturally translate it as "the old one".

Why is it modelo nuevo instead of nuevo modelo?