TV’s top comedy, “The Big Bang Theory,” was Thursday’s No. 1 program in all categories as it wrapped its eighth season, but it was down more than 20% from its year-ago conclusion. Elsewhere, ABC’s “Grey’s Anatomy” was down from the last couple of weeks but tied with skedmate “Scandal” as the night’s top drama, while NBC’s “The Blacklist” rebounded from its week-earlier series low.

According to preliminary national estimates from Nielsen, “The Big Bang Theory” averaged a 3.5 rating/17 share in adults 18-49 and 14.3 million viewers. It was up a little from last week when it went up against the NFL Draft. It dominated its timeslot, beating the combined 18-49 scores of the next two closest programs in the timeslot (“Grey’s Anatomy” and “Bones”) but it will finish down more than 1 full ratings point from last year’s 4.9 for its finale.

“The Odd Couple” didn’t do a lot for its renewal chances with a pair of original episodes at 8:30 p.m. (1.8/7 in 18-49, 8.5 million viewers overall) and 9 (1.5/5 in 18-49, 7.0 million viewers overall). The former was down about 10% from last week while the latter was off more than 20% from last week’s season finale of “Mom” in the timeslot. The lower 9 p.m. rating trickled down to the 9:30 p.m. “Big Bang Theory” repeat (1.4/5 in 18-49, 6.9 million viewers overall) and “Elementary” (1.2/4 in 18-49, 6.9 million viewers overall).

CBS tied with ABC for the night’s lead in 18-49 while pulling ahead in 25-54 and dominating in total viewers.

At ABC, “Grey’s Anatomy” (2.2/8 in 18-49, 7.9 million viewers overall) was down 15% (0.4) from last week’s two-hour episode, placing second for the 8 o’clock hour. “Scandal,” back from a week off, was on the low side at 9 p.m. (2.2/7 in 18-49, 7.4 million viewers overall), down a tenth from its most recent original. It figures to join “Big Bang” in showing sizable year-over-year declines for its finale, which is next week; last year, when it aired at 10 p.m., “Scandal” closed its season in April with a strong 3.4 rating.

NBC opened with a repeat of “Law & Order: SVU” (0.6/2 in 18-49, 3.3 million viewers overall), followed by “The Blacklist” (1.4/5 in 18-49, 6.7 million viewers overall), which bounced back 0.2 from last week’s low opposite the NFL draft. Last week’s “Blacklist” had its biggest-ever percentage gain in Live+3, doubling its same-night rating (2.49 vs. 1.25). “Dateline” (0.8/3 in 18-49, 4.9 million viewers overall) was down a bit from last week in closing out the night.

Fox had its strongest Thursday in a while thanks to a two-hour episode of “Bones” (1.1/4 in 18-49, 4.5 million viewers overall), with the veteran drama up a tick from its hourlong average last week. Its second hour was up a big 57% (0.4) from last week’s “Backstrom” finale.

And at CW, “The Vampire Diaries” (0.6/2 in 18-49, 1.3 million viewers overall) was up a bit while “Reign” (0.3/1 in 18-9, 1.0 million viewers overall) was steady.

Preliminary 18-49 averages for the night: ABC and CBS, 1.8/6; Fox, 1.1/4; NBC, 0.9/3; CW, 0.5/2.

In total viewers: CBS, 8.4 million; ABC, 6.5 million; NBC, 5.0 million; Fox, 4.5 million; CW, 1.1 million.